I know that files are interchangable, and can be opened in other app from menu, but sometimes it's overkill IMO.   When goal is to make some quick edits in one photo while document contains dozens of them, more convienient way would be just edit this particular image. Something like: select bitmap -> edit in Photo -> do what you want -> save directly back to Designer.   Same thing could be useful in reversed situation: select vector object -> edit in Designer