I tried to move stacks between albums and noticed this is not possible, is that correct?
It would be very convenient to be able to move stacks between albums, e.g. to an album once the work on the stack is finished.
You're correct, right now you can only move images, not stacks. There's no technical reason behind this, just an omission. Moving a stack would move the images inside it as well of course. I agree this could be useful.
This issue was resolved in Observatory 1.4.3. You can move and copy stacks between albums.