Import Cover Art source folder

I’m guessing the source folder for the artwork has to be the same as the file the .mp3 is in, right?

How do you import the cover art?
If you do it with an action, you have to specify a format string which in the end leads to a unique filename.
The filename could be a relative one or a fully qualified one.
see e.g. here:

The search words "cover art" show a fair number of threads

I’ve set up 2 actions - 1 to export cover art (filename: %artist% - %title%) and 1 to import cover art (again %artist% - %title%).

But since the import action doesn’t specify a path, I’ve assumed the artwork has to be in the same folder as the corresponding .mp3.

?

it has to be %artist% - %title%.jpg
And yes, the export leads to files in the same folder as the (current) audio file.

Let me give you a little background.

I accidentally deleted all of the art work from my music collection. But, I have a back-up with 90% of that collection with the artwork still intact. I want to export from the back-up, and import to my current library of tracks.

BUT - the folder structures are different...

I did a highlight all (~5000 .mp3's) and ran my export action.

MP3Tag exported the images to different filetypes (.png, .jpg, .giff, .bmp), and there were roughly 1000 files created that didn't have a file extension...

If I re-export with the .jpg extension in my action, will those files without an extension be rendered as .jpgs? Becaase, right now, they have no extension and I can't open them...

No, MP3tag only imports the files, it does not modify them in any way.
Even though other graphic types seem to be allowed, I would recommend only png and jpg files. bmp, gif and tif consume a lot of space, I would transform them now that they already in the file system.
If you have files that lead to picture files without extension, then something is wrong as apparently the mime type has not been saved correctly. Some kind of file corruption can be suspected.