I'm running MacOS Mojave on a 13" Macbook pro with a 4K external monitor (scaled to 2560 x 1440).
When running two apps in split full screen mode it won't let me reposition the "split" which controls the share of the screen of the two apps by grabbing the vertical bar.
This behaviour can be seem in this screen recording.
Any ideas on how to solve this? Or is this just a bug that needs fixing?