U3415W - change 50/50 setting for dual operation?

Is it possible to change the fixed 50/50 screen distribution between 2x connected windows hosts connected to? Actually I would like to have a wider desktop (HDMI) and a smaller one (DP). Unfortunately I need both set to 1.600x1.200 resolution, so both displays are shown correctly.

More or less, I would prefer to have 1.920x1.440 on the "right" half (HDMI) and 1.400x1.050 from the DP connected laptop, which may be scaled to fit in the screen space available. Any ideas, how tis could be set up/configured?

Host 1: Lenovo T550 (Win 7) / Host 2: Alienware 15 (Win10)