In Maia you can quickly look up a value in a debugger session by hovering your mouse over it (which is very handy for text values, for example):
When you need to browse through a large tree of values, this popup can be set to appear only after you invoke it.
The trick is that it is still viewable, but only when you hover mouse over a value holding the Alt key. Hitting Alt when the popup is open hides it — but that’s what you probably have already guessed.
There is also an option in the Settings dialog: