There is now hotkey as described in Customizable keyboard shortcuts to toggle active visibility for 'File Explorer', 'Search', 'Tags', 'Starred' - #4 by malecjan
While active~focused, the pane can be closed again e.g. by Ctrl+W
Can this request be archived or is there still missing something?
Hiding minimized sidebars mentioned by @sirentian in the post above is also discussed in dedicated request: Utilize wasted screen space along right edge