Newbie asks how to add title to a folder/directory?

Hi: My issue is I have several mp3 folders on a memory stick.
I play the memory stick in my car radio.
Not all the mp3 folders display the name of the folder.
Do I do a bulk change of all files album name in the folder or is there a tag for the folder name?

A tag is part of a file - so it cannot have a folder name.
What do you mean by

How can a folder not display the name of a folder?

If you want to move files to a new folder use an action of the type "Format value" for _directory.
Enter as format string
If you want to have the album name as folder name.

Sorry, I have not provided enough detail.
When the folders are on my PC, they have a name,
when I put the memory stick in my radio, a couple of folders have names,
but most have a sequence number only, no name or label.
The PC folder name is not matched by the radio folder display name.
I have assumed there is some sort of tag for the folder display name on the radio?

Which fields are filled in your files (check with mp3tag)?
Try to fill
%albumartist%, %artist%, %track%, %title%, %album%

Then see how you car stereo behaves.

PS: as I said: a file cannot have the properties of a folder. The whole thing with filenames and folders is a problem of the filesystem and not of the tagging.

Thanks, I will give that a go.
I naively thought folders had their own tags.

MP3tag has some filesystem related variables that follow the same syntax (with the % characters) as the field variables.
But actually, they refer to external data (like the filename or the path) as sometimes these properties offer data that can be used for tagging or that should manipulated to address the correct place for storage.
So far, I assume that your car stereo does not look at the (fully qualified) filename but checks the tags. And depending on that data it displays the tracks.