Use collapsed arrow for OptionButton and EditorResourcePicker

[programneer]

Describe the project you are working on

Modified fork

Describe the problem or limitation you are having in your project

The OptionButton itself.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

When one of these OptionButtons has opened, the arrow will change to the top direction.
It also happens with EditorResourcePicker.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Here's an video made with an modified version to include it:

test-arrow-up.mp4

It only demonstrates OptionButton but whatever

If this enhancement will not be used often, can it be worked around with a few lines of script?

No.

Is there a reason why this should be core and not an add-on in the asset library?

Impossible for add-on.

[Mickeon]

Not much of a UX design person myself. Is there other software that does this as well, as an example?

[KoBeWi]

Describe the problem or limitation you are having in your project
The OptionButton itself.

How OptionButton is a problem?