We fixed this for Maxwell 5, but later we changed the way we load the pymaxwell5 module. I have checked that Pymaxwell Editor is pre-loading the pymaxwell5 python module, and it doesn't. That's why the help is not working properly. To workaround this, just run a script that loads the module when you open Pymaxwell Editor:
The help module is populated the first time you hit "PyMaxwell Module Help" in the menu. Following times, that help is in the application memory. So, you need to run "from pymaxwell5 import *" before the first time you ask for PyMaxwell Module Help. Otherwise, the "empty help" was already loaded and you will need to close Pymaxwell Editor and open it again.