@basj How could it be an "incompatiblity" with the app? It is a normal win32 app so that should make it work normally, no? It is not installed though but is a standalone app like portable, is that a reason maybe?
What about the other issue? With that I actually mean the following:
1. open notepad.exe with txt1.txt
2. click tab button with that window in focus
3. it opens another notepad instance again with txt1.txt
That is totally not the desired behavior.