That might look conveniant, and I am not at all against it, but that wouldn't be sufficient anyway.
A project can be a subproject of more than one project. So expanding the rest api (projects) with
"Add subproject" (alike "Add version") makes a lot of more sense.
Ok, that's two api calls against possibly one. But I can't see a use case, where this would be a
real issue.
I'll provide a pr soon.

PR by @obmsch: https://github.com/mantisbt/mantisbt/pull/1453

thank you, @obmsch, by the way ;)

thank you, @obmsch, by the way ;)

thank you, @obmsch, by the way ;)