Here is the command related information from the latest Windows release to date:

Command language
-----------------------------------------------
A rich and flexible command language is supported via the
command-line, and command-line arguments can be combined.
Where appropriate, a specific display can be targeted by
prefacing the command with the monitor EDID serial number 
or enumerated display number, e.g., "2:AutoSetup"; if a 
display serial or enumerated number is not specified the 
command will be applied to the current selected display 
or to all displays, as appropriate. Commands include:
 
SetActiveInput [DVI2/HDMI/DP2,etc] - switches active input
RestoreFactoryDefaults - restores factory defaults*
AutoSetup - executes an autosetup (analog only)*
RestoreLevelDefaults - restores level defaults*
RestoreColorDefaults - restores color defaults*
SetBrightnessLevel X - sets brightness to X% (0-100)*
SetContrastLevel X - sets contrast to X% (0-100)*
SetNamedPreset [Movie/CAL1,etc] - changes the Preset mode*
SetPowerMode [on/off] - sets the display power mode*
SetOptimalResolution - switches to optimal resolution
SaveProfile [Name] - save settings to named profile*
RestoreProfile [Name] - restore settings from named profile*
DeleteProfile [Name] - delete named profile
SetGridType [X] - changes Easy Arrange grid type to X
Rescan - rescans display hardware
ForceReset - reconnects and rescans display hardware
SetControl X Y - sets hex control X to hex value Y
IncControl X Y - increases the value of control X by Y
DecControl X Y - decreases the value of control X by Y
SetPxPMode [Off/PiP/PBP Main Sub1] - set PxP mode/inputs
Zoom - switches between PxP and fullscreen mode
Wait X - pause X milliseconds
Exit - terminates the program
 
Some of these commands require familiarity with the MCCS
standard. For example, on monitors that support it the 
command to switch the OSD language to Spanish would be 
"SetControl CC 0A"; to unlock an OSD that has been 
inadvertently locked "SetControl CA 02".

Instructions can be combined on the command-line, and
assigned to standard Windows shortcuts with optional 
hotkeys or coupled with the native Windows Task 
Scheduler to execute at certain times.

For example:
 
  "ddm.exe /RestoreLevelDefaults /2:SetContrastLevel 70"
 
would first restore level defaults on all monitors, and 
then set the contrast level on monitor #2 to 70%. 

  "ddm.exe /G606K4NP0:SetPxPMode Quad DP1 HDMI2 HDMI1 DP2"

would target the monitor with service tag/serial number 
"G606K4NP0", turn PBP-quad on, and set the main window 
input to DP1, and the three sub window inputs to HDMI2, 
HDMI1 and DP2 respectively.

Note also that the serial number or service tag is the one 
provided by the monitor EDID, and may be different from the 
one affixed to the back of the monitor. The EDID serial 
number can be found in the DDM About box, and in the 
shortcut created from the DDM monitor service menu: while 
holding down the SHIFT key, click on the DDM About button 
and then select "Create shortcut" from the popup menu.

NB: If not targeted to a specific monitor, commands listed
above that are tagged with an asterisk (*) apply to all
monitors to facilitate simple and uniform control over all
members of a multimonitor matrix. For instance, if executed
on a matrix of 16 similar monitors, the command-line:
 
  "ddm.exe /SetNamedPreset Warm /SetBrightnessLevel 75"
 
would set all 16 monitors to Warm preset mode, with a
brightness level of 75%.

Tip: you can use Shortcuts app on macOS and use a Shell script to execute these commands.

This way you can invoke them from your Touch Bar, Siri, keyboard shortcut, Finder, menu!

Note: some commands do not seem to work, a.t.m. I can disable PBP, but not switch to PBP.

E.g. To disbable PBP I am using this Shell script in Shorcuts: 

/Applications/DDM/DDM /SetActiveInput Thunderbolt /SetPxP Off