suggest:
1 - select Project File Tree-> Multile Files(SHIFT + left Click Mouse to select),
right mouse to remove files?
why remove only one file???
and the other pop menu to make one file only!
2 - How to set Tools to select that files which I selected multile files?
i couldn't find the List of available built-ins to do it
(eg: $(ACTIVE_EDITOR_FILENAME,...))