Artist - Album Artist

I have a music library that I've been accumulating for nearly 30 years now - so literally gigabytes if not terabytes of data here. I'd like to get all my metadata consistent across everything and some of my music tag data populates the Artist field, but not the Album Artist field. Others do the inversion (Album Artist but not the Artist). Some even have different entries in each column!

In the interests of simplifying my storage, I'd like to have the two fields match one another. So Artist = Album Artist.

Is there a macro way to make this happen in MP3TAG? I am a contributor to the program, as I appreciate the efforts the developer has done here, but there's still a few things I don't see that I'd like to see happen (this being one of them).

To fill the empty one from the other with content isn't that complicated with Convert -> Tag to Tag

But which tag content would do you choose/prefer, if you have two differente names like in this example:
Artist: Abba
Album Artist: Bruce Springfield

Never mind, figured out the Action format:

Format value "ALBUMARTIST": %Artist%

I found it useful to my players(plex and synology) and organization in general, to organize like this:
Album artist: the album artist(if many: Various Artists)
Artist: the artist itself

i always create both because the software goes to album artist first.

Sure, but the OP wrote:

If you have different artists in the column ARTIST and the column ALBUMARTIST it will be tricky to fill them correctly.