OK, so the “blue arrow” is to get the focus top right of the menu bar – I now know that’s called the “status menus”.
Doesn’t appear to be working this side, possibly because of Barkeeper 3 – but given the latter, I don’t need to use it, and that mystery is solved.
The “red arrow” changes how the Tab key selects either only text fields, or jumps between basically all clickable fields inside a menu window. Had this activated all along, to allow for Tab to jump between all, but didn’t realise this was related.
The “green arrow” had me doing some digging, since I found plenty of sites explaining the shortcut, but not what it actually does.
Finally found a description of the “window drawer” being those pop-out menus that some older(?) Mac apps (like Pathfinder and Nisus Writer Pro) used to use… Haven’t had a need to use one in ages, so it slipped my mind what they were.