actually the split screen menu features 4 items:

Synchronization >
--------------------
Open Multiple Series
Split Series
--------------------
Window >


I thinks that instead of the "Window >" item it would be much better to move all it's submenu items up one level...

I mean:

Synchronization >
--------------------
Open Multiple Series
Split Series
--------------------
Close active panel
Close all panels
--------------------
Series preview bar
Toolbar and status bar
--------------------
Full screen mode


IMHO all the Window submenu items are very commonly used feature and having to click twice on the UI (first click to open the Split screen menu; second click to open the Window submenu) in an unnecessary annoyance

Thanks for your suggestion. It seems to be a good idea.

should be an easy hack, isnt't it?

Sure, a few lines of code :-)