Tim Hoffmann - 2015-02-17

Session files are just a way to store part of the editor state for later reuse.
There is no notion of session in the editor itself. It just has a current state, but
it does not know where the state comes from. Therefore, "Save Session" has currently no meaning.

That said, your request in itself seems reasonable, but would require some restructuring
to introduce the concept of an active session. I assume that we won't have time to work on that any time soon.