Thanks for your reply. I looked at your link, and my head is aching! Wow, a 72-character GUID!! It looks like trying to remove the duplicates may be a lot more work than I want to do, given current tools to assist me.
The column I tried duplicating is a file dated 1999 on my server. I assume it didn't have a GUID originally. Somehow the copy process must have created a new GUID.
The Bench and Seat are dated 2008. They must have the same GUID.
Of course I have no idea what the subtype of each of these parts is, and it would take more effort than it is worth to open the library parts two different ways, as mentioned in the article, to track this down. I have been living with duplication errors in my loaded libraries for years, and it hasn't been a real problem, so I guess I can live with it for a while linger.
Wish list: it would help if ArchiCAD could give me information on specific pairs of duplicates, with the file path for each. That way I could better track them down without going into the arcane world of library part creation.
R Muller
AC 28 USA (20+ years on ArchiCAD)
MBP 64GB Apple M1 Max OS 15 Sequoia