OK, I don’t know javascript but I can scratch a bit of python.
I created a script that keeps all the my pseudo-tags and related hash in a dictionary. Then, it sweeps all the note files looking for my pseudo-tags on the form of tag:<tag name> and write the hash after it in case it is not already there, which gives me tag:<tag name> <tag hash>. The script also updates the modification time of the note so that Joplin sees it.
Now, I just need to write the tag name in my “human readable” format above in the body of the notes and I then run the script to automatically add the hashes. For searches, I still use the hashes as mentioned in the 2nd reply of this thread.
Surprisingly, it seems that no information about the tags are kept in the notes themselves for the current system of Joplin.