Saving a menu as a reusable template or an entity of sorts would be super helpful with how Layouts are used. I have a few layouts setup based on user roles, as well as page workflows where some more privileged users end up moving between layouts.
This causes me to maintain multiple menus - making sure to keep identical menus for some user roles between layouts. If the menu changes at all, I have to rebuild more than 1 menu (see also: https://community.tadabase.io/t/sub-menu-drag-and-drop-organizing/108/3
I could see this working as editing/building a layout, when you select the menu component, you are prompted to select a menu to use, or create new.