Palette tree should be a single tabbable object
As discussed in https://musescore.org/en/node/296153 (see suggestion 5a).
Navigation within the tree should be done solely with the arrow keys. The user should be able to return to the searchbox at any time simply by pressing Shift+Tab once. Pressing Tab again should put the user back in the tree on the same item as they were on before they pressed Shift+Tab.
Currently all objects are tabbable. This includes all palettes, palette elements, expand/collapse arrows, three-dots buttons, and so on. navigating the entire palettes tree can easily involve pressing the Tab key 50 times or more. The search feature can help to reduce this number considerably, but the situation is still far from ideal.