ISRC and TMED are included in the list.
You can create user-defined fields with any name.
What would be the standardized field name for the data you are looking for?
See e.g. for standard fields: http://id3.org/id3v2.3.0
hi
i would add to my songs , just because sometime i burn my audio on a cd
and i would like to create a cue-sheet with all these flags
about these flags even eac doesn't read all , i guess only cuetools cue ripper can read them all
but i don't want to make a collection of cue sheet files
I am not sure if you got that right with the fields. The id3-org site shows you all the tag fields that are defined by the standard.
If the information you try to save is not covered by a tag field mentioned on the id3 org site then it is already covered by the option to create user-defined fields.
The "4 track" stuff is part of the TMED field - so that is already available in MP3tag.