In the editor window, I can "clean up" the view by pressing the escape key: any bottom tab that is open will be closed. I use that feature extensively while editing code.

In the form editor however, when pressing escape key, the editor switches to the XML version of the .ui file instead of closing the bottom tab. For me at least, that is very frustrating behaviour as I am used to pressing the escape key to make room for editing.

I don't know whether the switch to XML code is a deliberate feature, but if it is my suggestion is to first close any bottom tabs, and only go to XML mode if no tabs are open.