Oblio
1
The help file indicates that this might be possible but I can't make it work.
e.g. If I have a user-defined field named $123 containing text "ok"
$123 HAS ok
$123 IS ok
$123 MATCHES .?
$123 PRESENT
Nothing works. Same for %123. Maybe it is not possible?
https://docs.mp3tag.de/filter
For the $123 it should be
%$123%
Oblio
3
Thanks ohrenkino! That works.
How about %123 ?
I think that this an illegal fieldname as the % is a reserved character.
Oblio
5
I think you must be right 
Maybe Florian can update the help file.
Or make it work e.g. by escaping the % by using %%
So for %123 you use %%%123%
Please accept this feature request.