Does anyone know how I can merge/deduplicate contacts in a .vcf vcard file?

Tonto2 is a python 3/Qt graphical app that runs on desktops. It’s main purpose is not to manipulate *.vcf files, but the appendix to the instruction pages tells how, anyway. Tonto2 uses a spread-sheet-like presentation paradigm. With appropriate magical mystical spells, you can import *.vcf as *.csv and sort the *.csv by last-name, phone-number, eMail, zip-code, or whatever. It won’t de-dup, but you can spot the duplicates easier once they’re collated next to one another in one sequence or another. Show just the significant attributes. Probably you’ll want to sort, look, sort, and look again. Killing entries is nearly as simple as checking them off. FAIR WARNING: This process is time consuming, frustrating, and fraught with peril. Keep several versions of your address list until you’re sure the final is the one you want to keep forever. My experience is that I always find stuff I want to keep in each of all (sometimes more than two) duplicate entries, so deleting the dup’s is not what’s called for. Merging means manually copying from one entry and pasting into another. Due to the judgemental nature of how to handle conflicting and out-of-date info, I’ve hesitated to try to automate the process.

Maybe copying/moving files using a file manager?

<plugging package=“file_manager”>FileZilla</plugging>

-or-

<plugging package=“file_manager”>Gnome Commander</plugging>

…but call me quaint. I still like…

<plugging package=“file_manager”>mc</plugging>

… 'cause it always just works. mc can ostensibly preserve attributes, time-stamps, and (with appropriate privilege on the receiving end) ownership of transferred files (using an sftp server supposedly).

I’m not familiar with jabref, so I probably shouldn’t stick my oar in here. But I will anyway. I’ve written my own python script that I use for lists like Web bookmarks. It’s a poor man’s database manager, so you can add attributes to bookmark entries and sort and search on those attributes.