I understand that this might be a feature, to quickly remove tabs from the parent window. However, it is not ideally to have to click two buttons; first click the the collapse button; then click the delete button, just to delete a single window. If it is a feature to remove tabs from the window then please add a button for it, and make the delete work as it should.
I wasn't sure if this is a bug or a feature, to me it looks like a bug. if it was a feature, then I would assume it would be clear that the button will delete the window without the tabs.
Customer support service by UserEcho