Use dedicated symbolic for dropdown with mutually exclusive options.
Currently drop-down menus use the GTK_ARROW_DOWN symbolic regardless whether the pop-up opens a menu with actions or a list of options like a combo row. Apple introduced an up+down arrow on its platforms some time ago for dropdowns with mutually exclusive options (https://developer.apple.com/design/human-interface-guidelines/pop-up-buttons).
Adopting this would more clearly differentiate a list of options from a menu with actions especially with the flat header bar style of libadwaita. It could also be used in combo rows where it would remove the mismatch of the downward pointing arrow and a menu popup that can also appear above the row.
Edited by Philipp S