Isn't there a way to merge two user accounts on a Mac? Or, to migrate all of the data from one user to a new user?

A few months back, I was having problems with my 2021 M2 Pro 16-inch MacBook Pro running Monterey. I have always had an admin user that I don't really use on a daily basis, and a STANDARD user that my documents live in and are organized in.

So, I created a third user, a new STANDARD user, that has a slightly different name (this one includes my middle initial) and then set up my mail accounts and migrated my browser favorites and documents, etc.

This arrangement got rid of the sluggishness that I had been experiencing, but it's a hassle, because there is still some important user-specific data in the old Standard User that I didn't manage to migrate.

I seem to remember a way of "merging" or "consolidating" two user accounts, but it's been years. I think this method included a way to resolve any duplicates that arose. Of course, if there is some bad corruption of some kind in the original standard user, I don't want to move it into my new standard user.

I don't have any applications that are in USER/APPLICATIONS. They are all in /Applications and available to all users.

Any ideas? Thanks in advance!