Well first thing is that the label actually does not do anything.
it is just there for operator convenience.
soo i guess the thing you realy want to change is name or both label and name.
I don’t know if you have developer skills but a way to do it is to save the playlist. make a litlle helper program that change’s it and load it back in again.
There is also a repository functionality which actually could be nice for your workflow.
But it is very badly documented. and a bit fiddly see