Can't Open List boxes with Arrow keys or Alt + Down

Issue type

UX/Interaction bug (incorrect behaviour)

Bug description

Assume the focus is on a drop down list box (combo box). e.g. the format in the File → Export dialog - there are many examples.

Expected behaviour is to press Arrow Down, Space or Alt + Down to open the list.
Actual behaviour:
Only pressing Space or Enter seems to open the list.
This is misleading as pressing Enter should normally activate the "default button" in the dialog.
It is then necessary to press space to select the required item, usual expected behaviour is that when you tab off the combo box whatever you were last on is selected. But as tabbing jumps over multiple items (see #20056) it is necessary to press space to I assume close the combo box before you can arrow down again. This is unfamiliar behaviour to most screen readers.

Steps to reproduce

1. Go to File/Export
2. Tab twice to get to the file output drop down list.
3. Arrow down and instead of the combo box opening you are on the next radio button.
4. Arrow back up to the combo box and press space.
5. Arrow down to select an option.
6. Press Tab to jump to next item and out of box, instead it jumps over all the other options to the export button making the user think there are no further options (see #20056)
7. Arrow back to the combo box and this time after opening and selecting the item press Enter. Expected behaviour is that the dialogue would close as Enter should trigger the default button, in this case export. Note that Enter just closes the combo box. Enter is not usually used for opening and closing combo boxes.

Screenshots/Screen recordings

No response

MuseScore Version

4.1

Regression

I don't know

Operating system

Windows 10 with NVDA

Additional context

No response