Completely fair to complain that the icons do not indicate the purpose of each menu. They do helpfully name each menu in the tooltip: the hamburger on the left is "Main Menu", the three vertical dots in the location bar is the "Current Folder Menu" and the down arrow next to the view switcher is "View Options".

The Main Menu offers global actions, and appears in the left-hand global pane of the window. The Current Folder Menu offers actions specifically related to the location named in the location bar. The View Options menu is part of a split button with the view switcher, and has additional view-related options.

You're right that the icons themselves do not explain their full and complete functionality. Fortunately, we do not need to rely on hoping for the right labels for actions (be they textual or iconographic). For software intended to be used on a regular basis, it's worth spending a bit of time internalizing the model.

Well, use another file explorer? Just because it's also developed under the same project, how does it have any relevance here? Especially that on Linux the file browser has no special status as on e.g. windows.

Ctrl-T.