be able to close all popup windows when running musescore without window manager

MuseScore can run with without a window manager. But I always run into a problem when I open the synthesizer window, because there is no way for me to close the synthesizer window after opening. And since the window will popup at the top-left corner (coordinates 0,0), it will cover the top menu, preventing me from closing the window without killing mscore. Most of the other popup windows either have a "Cancel" or "Close" button in the gui, or have a shortcut key, e.g. F10 for Mixer, which I can press a second time to close the Mixer window. So basically for this feature request, I would make sure there is atleast one of the following (but preferably all):

1. A cancel or close button.
2. A keyboard command that will close the window. (For something like synthesizer which doesn't have a dedicated function key, it would be nice to atleast be able to use a shift or ctrl + function key).
3. Allow the window to be dockable, like palette & inspector, so it won't appear at top-left corner of screen.

This use case for this is if want to running musescore inside android via a plain X-Server like XSDL, but don't want to deal with overhead of a window manager.