Ahhh I see now, totally overlooked it at first — we don’t show the minimize button until a message is sent. So if I click on the + in the sidebar to start a new personal chat, I get the window with the ability to add people, and that hides the minimize button.
Then if I send a message, it appears again
So we should update this so the minimize button is present in while editing users. Thanks @ProjeDEV!