Access custom tags from files with tagger-script

Right now it is really easy to write custom tags with taggerscript, but I could not find a way to read them from the file. I’d like to have a plugin that can make any custom tag available in taggerscript that is present in the files. So that eg. $getcustomtag(whatever) returns the value for that custom tag if it is present.

Is this possible with a plugin?
If yes, as I am not a coder and I am not familiar with the plugin system in picard, how would I tackle this problem? I know that writing a plugin without coding knowledge is a problem as was pointed out to me, but maybe this is not too hard to implement, then maybe even I could get this to work with some help.

I think this should already work, not sure if it works in all formats. I think if you use e.g. Vorbis or Ape tags, where tag names are just arbitrary strings, you should also get all the strings in an equally named variable (all lower case in Picard). So if you save %mytag% and read this file again I think you should be able to have a %mytag% tag again.

For ID3 this should work likewise: Every tag Picard does not now about it saves as e.g. TXXX:myname, and it also again loads all TXXX tags again and makes them available as variables.

Doesn’t saving %mytag% and reading it again as %mytag% work for you?

no, at least if I am misunderstanding something. But Tags & Variables — MusicBrainz Picard v2.11.0rc1 documentation suggests that only those defined fields are available.

$set(test,‘xyz’) > xyz will be written to custom field test
$set(%test%,‘abc’) > nothing will happen

$set(test,%existingcustomfield%) > nothing will happen
$set(test,$get(existingcustomfield%) > nothing will happen