Figured I’d move this into Ideas since it’s a new feature request.
Each route does have a GPX download - it’s in the vertical three dot menu. You can extract the coordinates from that file.
I’m not sure that this is what you’re really looking for, though, unless you are building routes node by node as opposed to intermittently clicking & letting the auto-route get you from point to point.
I’d suggest voting on Automatically Generate Routes since that idea originally got shot down as something people didn’t want … but lately I’ve heard more requests for it or something like it.
I don’t know how far in you plan on going, but I’d also recommend not obsessing over route efficiency. Overly efficient routes can get silly complex in a way that cannot be fun to run.