Hi Stefan,
yes, probably you are right...
It is at all not very clear... There are two commands:
Remove in context menu of Project Pane and "Remove current file" in Project menu. Even I do not know without checking the code are they are same or different

As far as I remember, there was some logic that takes current open file as source file if no file is selected in project pane... But I think this is very confusing... So probably I will at all remove entry from project menu or just decide that this is different command, that only works with currently open file.
What do you think?
The problem you have reported is bug for sure. I will fix it in beta 1.48.
All functions should work even without save of project. And I see also bugs on adding current file to project in context menu of editor (it should be always suggested if file is not in project and project is not initial).
Best regards,
Alex.