Comment 1 for bug 2004587

One way to do it to preserve backwards compatibility would be to have marc_export (and Supercat) add the owning library and circulating library to new, additional subfields while still retaining the two 852 $b.

The tradeoff would be the result permitting fewer items to be embedded in the MARC record before running into the ISO 2709 limit.

Alternatively: add command-=line options to marc_export (easy) and library settings for Supercat output to tune this, though the more options we add, the more that going to the effort of creating item record MARC embedding templates would be desirable.