Hi,
when I edit project files by hand (i.e. right-click->open with), #D shows a dialogue to selct the editor. Since .*projs are xml, I leave it at the default.
#D now opens a new instance of the buildin xml editor - even if there already was one.
I'd be happy if double-clicking a project would give me the xml via default-open, which would have the nice side-effect of keeping the editor instance.