After starting to set up an e4 based RAP application, one of the thirst things that popped into my eyes was the Windows in Windows Problem. That is, you have your browser opening the e4 rap application and you see a window title (which effectively exists for both Window and TrimmedWindow) which does not make much of a sense. For RAP based on 3.x here is the solution. For e4 based RAP it required some investigation, so here goes the solution.
Add a TrimmedWindow or Window element, and provide the tag shellMaximized and the persistentState value styleOverride (thanks to Lars Vogel for pointing this out) where the value is determined like you would set it programmatically with
int val = SWT.NO_TRIM; System.out.println(val);