I have a small issue, but I think it’s still worth mentioning.
The ComboBox class seems to be missing a colour ID for its outline when in focused state.
Other components do offer it, like for example TextEditor::focusedOutlineColourId, but in ComboBox I can only specify the outline colour while not in focus via ComboBox::outlineColourId.
So in the screenshot below, I have set the regular outline to black, but I have no way to change the gray outline shown when I open the ComboBox.
I know I can just subclass it and override the paint method, but this just seems like something that was overseen or forgotten