Hmmm. Looks like I posted to the wrong thread! Here's a slight re-write of what I posted to
https://discussions.apple.com/thread/252935863
Well, here's what I've come up with to date (with a few questions at the end):
Method 1:
This is the worst of the bunch.
Enable Mousekeys.
Move the highlight bar to the desired file using the up and down arrow keys.
Move the mouse pointer to the Add Tags or Edit Tags control using the keys on the number keypad. The problem with this is that it is slow and painful.
Press keypad 5. And again, the Tags menu comes up and can be worked without the mouse.
Method 2:
This is the best I've come up with so far.
Move the highlight bar in the Finder with the up and down arrow keys. (Tech tip: Use Opt-Up or Opt-Dn to move the highlight bar to the top or bottom [first or last file]. This works on many other lists, like in menus and Mail.) It'd be nice if PgUp and PgDn would move the highlight bar one screen, but alas, it only moves the list itself. Arghhh!
Press F5. (You might have to set this up in Sys Pref, Shortcuts, Move focus to the window toolbar, press Enter, press F5. ^F5 is the default.)
Tab over to Edit Tags.
Since the control is outlined, press the space bar.
And voila`! The Tags menu comes up and can be worked without the mouse.
Method 3:
Probably the best, except that it doesn't exist.
A keyboard shortcut that right-clicks the highlighted file. Unfortunately, you can't set this up with macOS.
>>> Please keep in mind that I want the right-click menu (aka context menu) to come up for the file that is highlighted, NOT whatever is under the mouse pointer. This is a crucial difference!!! So I'm not really fond of Method 1, even though it completely avoids the mouse. <<<
Might Quicksliver or Alfred do the right-click on the highlighted file bit? I already have Quicksliver. It comes up when I fat-finger the shortcut for it. I don't know where it came from. I don't recall ever downloading it, although I might have downloaded it years ago. Just checked and found that System Information lists it as being from an "Identified Developer". But previously I've always been afraid to set it up. So it should be safe?
What's the best option for setting up a keyboard shortcut that right-clicks the highlighted file or control? Quicksliver? Alfred? Something else?
If there were just one thing I could ask for with macOS, it would be a native right-click the highlighted file keyboard shortcut.