Help making filename ALL CAPS

with an action (without having to type [replace "a" with "A"]) etc? THANKS!

try an action of the type "format tag field" for the pseudo-tag "_filename":
Enter as format string
$caps(%_filename%)

I do not know whether some programs will like it. Windows does not distinguish upper and lower case, an iPod seems to be nervous if the extension is MP3 instead of mp3 ... So beware.

Mp3tag provides some possibilities ...

You can manipulate a filename by using the pseudo tag field _FILENAME.

Action "Format value"
Tag field: _FILENAME
Format string: $upper(%_FILENAME%)

Action "Format value"
Tag field: _FILENAME
Format string: $regexp(%_FILENAME%,'.','\U$0')

Action "Replace using Regular Expression"
Tag field: _FILENAME
Regular expression: .
Replace matches with: \U$0
Case-sensitive comparison:

DD.20100626.0510.CEST