How to hide file format (.mp3)?

In the FILENAME section Mp3Tag is showing file fotmat.
For example: SongName.mp3

How can I hide (.mp3) them for all files?

Enter as Value for the column definition
$replace(%_filename%,.mp3,)

(Can't imagine what it is good for)

$replace(%_filename_ext%'*','.mp3*',) ... or ... $replace(%_filename_ext%'*','.'%_extension%'*',) ... or ... %_filename%

See also ...
http://help.mp3tag.de/main_viewcolumns.html

DD.20160219.0933.CET