MuseScore 4.0 — For no apparent reason the Mixer lost its close buttons

I like the single-step option of closing the Mixer with a close button, like the familiar x in MuseScore 3. (In MuseScore 3 on MacOS the other option was to click the window's leftmost button in the upper left.)

Now in MuseScore 4 I have to:

    • click the "..." menu
    • read and navigate it
    • click the Close menu item

Call it just three steps now, but I think of it as three times the work.

I'm finding similar cumbersome inconveniences in other areas of the UI. More on this later.