I get the idea of focus-mode removing all the distractions to help you focus. But one thing that not even Sunsama can stop from distracting me is my own brain. It comes up with ideas and (other) tasks that need to be done and the only way to handle those distractions is to write them down as quickly as possible. Those braindumps are almost by definition tasks that need to be dealt with after exiting focus mode. And therefore it makes sense to dump them right into Sunsama.
So, what I'm suggesting is a button that opens a "new task" modal. The new task is automatically added to the inbox (not displayed on the focus screen).