[Koha] join/merge some tag 952 to only one

Hello people I have multiple fields in my 952 file and would like to put them together so I can track the number of copies before importing them into the database. for example I have: 952$a 952$b 952$y 952$9 and I wish it were like this: 952$a$b$y$9 but it's the only thing I can not do in the editmarc Has anyone been through this yet and solved it? Ana Bela