There is an is issue with GHPython editor that has been bugging be since the start of Rhino 6:
When GHPython editor window is maximized (to the full screen), its bottom is hidden behind the task bar.
Attached is an example screenshot.!
Rhino 6.13.19058.371, 02/27/2019
Windows 10 Pro, version 1809
This is not the case with my current PC. I checked and the same issue exists on other Windows 10 PCs, where Rhino 6 is installed.