The online U4919DW User's Guide page 52 only shows two PC sources PBP as side by side PC 1 Left 50%- PC 2 Right 50%. The DDM software only shows different layouts in its Easy Arrange. But those different layouts are only for one PC. So on the U4919DW, if using PC 1, the DDM Easy Arrange would only change the layout for PC 1 Left 50%. Then move to PC 2. Running DDM Easy Arrange would only change the layout for PC 2 Right 50%.
I got one U4919DW monitor. I connect it to two laptops. I am working on PBP format. However, the given option for PBP its only 50%-50% for each source. I wondering if there is another option to set different PBP screen split? I have seen in Dell Display Manager 2.0 that it is possible based on the software. 
U4919DW, different PBP screen split?