U4025QW and daisy chaining issues

The U4025QW does not have a DP out port. So no, you cannot daisy chain from the U4025QW when connecting to the U4025QW DP in port.

Desktop RTX 3070 DP out port --> U4025QW DP to DP cable --> U4025QW #4 DP in port

Desktop RTX 3070 #2 DP out port --> U2722DE DP to DP cable --> U2722DE #4 DP in port (MST On)
U2722DE #5 DP out port --> U2719D DP to DP cable --> U2719D #3 DP in port

I am very confused as to your Laptop setup.

According to the U4025QW User's Guide, it only allows TB4 daisy chain in this setup =

Computer TB4/USB-C video port --> U4025QW 1.5 M TB4 cable --> U4025QW #6 TB4 upstream port
U4025QW #5 TB4 downstream port --> retail 1.5 M TB4 cable --> second Thunderbolt monitor TB4 upstream port

Unless I just missed it, the U4025QW User's Guide never shows using a daisy chained second monitor DP in?

The U4025QW Menu --> Display even specifies Thunderbolt Daisy Chain = Optimized or Standard

What's confusing about the laptop setup? Let me know and I'll try to clarify.

It's a work laptop and private desktop, I'm on the laptop during work hours and use the desktop the rest of the time. My aim is to be able to easily switch between the two; no simultaneous use needed (besides maybe occasionally leaving the laptop plugged in and powered on while using the desktop). In general I'm trying to optimise the switching process, i.e. the least cable plugging in and out and the least button presses needed.

What I was confused about is the following:

• Laptop screen turned on: 5120x2160@60 + 2560x1440@60 + 2560x1440@60
• Laptop screen turned off: 5120x2160@120 + 2560x1440@60 + 2560x1440@60

I.e. the daisy chain works with just the TB 4 cable from the laptop to the 4025, but I'm only able to get 120 Hz on the U4025QW when the laptop screen is off - and I could be wrong, but my understanding is that the laptop's built in screen doesn't take up any of the Thunderbolt bandwidth, so this is a GPU, not interface bandwidth limitation.

Ideally I'd want laptop screen on and 5120x2160@120 + 2560x1440@60 + 2560x1440@60, not sure if it's possible.

As for the desktop, I'm looking at this page, and according to the Daisy chain connection matrix table, the "DP in, TB out" scenario should be possible (second row of the table). I think I have gotten it to work a couple of times, but it seems unreliable, and the 2722 doesn't seem to pass the DP signal to its DP out (so if it ever works, I'm only seeing the 4025 and the 2722, but not the 2719).

I'm also a bit confused about the Power button sync feature. I've set it up, but if I turn off the laptop while it's still connected, I'm unable to make the monitor wake up at all when turning on/waking up my desktop afterwards. If I turn on/wake up the desktop before turning off the laptop, it seems to work, but I feel this shouldn't be required (it makes things less flexible). Ideally I'd expect the monitor power button to only double the laptop's when that is the selected input, and function normally with the rest of the inputs.

@DELL-ChrisM2, anything new on the topic? Anything I need to clarify? I'm still confused.

Also, there seems to be an issue with auto input select. The feature is enabled on both the 4025 and on the 2722, and it seems to work well on the 4025, but I still need to manually select an input almost every time I unplug or turn off the laptop and want to use my desktop. Any workaround to that?

Without knowing the laptop display matrix table, I can only guess that when your laptop screen being on or off, it directly alters the total pixel count and data bandwidth your laptop’s graphics card must process. In a high bandwidth three-monitor daisy-chain setup, this small change can force your system to reallocate resources or lower refresh rates to prevent visual glitches.

The refresh rate drops on the U4025QW maybe due to these technical factors:

Bandwidth limits and data sharing

Daisy-chaining multiple monitors means all displays share the total bandwidth of a single video port (like DisplayPort or Thunderbolt)

• The laptop screen is ON: Your GPU treats it as a fourth display. Pushing pixels to four screens can exceed the maximum bandwidth of the cable. To compensate, the system automatically drops the refresh rate (e.g., from 120Hz to 60Hz) on the U4025QW monitor to keep the video signal stable.
• The laptop screen is OFF: This instantly frees up bandwidth, allowing the daisy-chained monitors to run at higher refresh rates.

GPU resolution and refresh rate caps

Laptop graphics cards (or the integrated graphics inside your processor) have hard limits on the number of total pixels they can push simultaneously. When the laptop lid is closed, the GPU's total available resources are redirected entirely to the external monitors. This change can trigger the OS to re-detect the hardware, letting it drive the daisy chain at the proper refresh rate.

DisplayPort MST limitations

Daisy chains rely on MST to send multiple unique video signals down a single cable. Because the MST hub within the U4025QW has to slice up the available bandwidth for all downstream screens, turning a laptop screen on or off forces the hub to renegotiate bandwidth. Many monitors will default to halving the refresh rate (or capping resolution) to ensure the chain doesn't drop the signal entirely.

Operating system and driver re-detection

When the laptop screen is turned on or off (or the lid is closed), the OS (like Windows or macOS) detects a hardware display state change and re-evaluates the projection settings (e.g., duplicate vs. extend). During this handoff, display drivers often revert to "safe" baseline settings, which can lock the U4025WE into lower refresh rates or force them to 60Hz depending on the graphics driver default.

Hopefully if any of these guessing matches with your refresh rate issue.  I think this is a common problem when you have mismatch refresh rate within a daisy chain setup.  I suggest to check your display settings, open your OS's display settings (e.g., Settings > System > Display) and manually set each of your daisy-chained monitors to the desired refresh rate while the laptop is in your preferred state (lid open or closed).

For example of Dell Pro Max 14 MC14250, it does not support direct graphics controller, direct output mode.  Therefore, the internal display being ON or OFF will affect the bandwidth and the number of external displays.

As for the desktop display issue, an RTX 3070 can support 1 monitor at 5120 × 2160 (120Hz) per DisplayPort. You cannot daisy-chain more than one monitor on a single cable at this resolution and refresh rate, as it exceeds the bandwidth limitations of the GPU's DisplayPort 1.4a.

You may consider to use other DisplayPort and HDMI port on RTX 3070 to connect to U2722DE and U2719D. 

@Chino de Oro​ Fair enough, this explains the limitation of the laptop.

As for the RTX 3070 and the bandwidth, maybe that's not entirely true. I tried setting the 4025 to 5120x2160@60 and I still couldn't get signal from the Thunderbolt out. By rough calculations 2560x1440@60 is less than 25% of the bandwidth needed to drive 5120x2160@120, so dropping that to 60 Hz should theoretically free up enough bandwidth - but practically it doesn't seem to work.

Going back to the two DP cables approach for the desktop, one more thing that's bugging me is that I have to constantly go into the 2722's menu and select the proper input when switching from the desktop to the laptop and vice versa - even if auto input is enabled (and, to add to that, there are cases when the computer detects an output there - i.e. I can move my cursor out the left edge of the 4025 (and Settings shows it where I expect it to be), but the 2722 doesn't detect that and still looks for signal on the USB-C input (and goes to sleep shortly after). And the 2719 I very often have to turn off and back on again from its power button before the desktop detects it. Annoying.

I do not have the same setup.  My comment was based on my knowledge, research, and calculation your hardware setup.  With the info I provided, only trial and error will get you closer to an acceptable ideal setup at this point. 

Not much progress, but still, thanks for the input.

I'm looking to swap my GPU in a few months, most probably with an RTX 50xx - so maybe in the meantime I could figure out the rest of the problems. If lowering the refresh rate on the 4025 to ease the bandwidth still doesn't make the TB out work, this means that there are other limitations besides bandwidth - and even if I get a GPU with a DP 2.1b, it's possible that I would face the same other (still unknown) problem even if the bandwidth will be covered.

I'm going with the separate DP connections for now as I don't have much choice.

Any suggestions about the input auto switch issue? It's still present (and annoying). Does it matter what display configuration I leave the desktop in? Now that I think of it, most of the time I'm putting it to sleep, it only has the 4025 active. Maybe I'll try turning on all three displays before sending it to sleep.

Follow up: I tried leaving all three displays turned on and enabled before putting the desktop to sleep, and they still don't wake up automatically after unplugging the laptop and waking the desktop.

Side note: today I spent 15 minutes trying to get all three displays to work on my desktop. I'm still going with the two cables approach and the exercise involved turning the monitors on and off multiple times, detecting them through Windows Settings, switching configurations and so on - all that for something that should've been two button presses. I know Windows is buggy, but I feel like there's a hardware issue to this too.