Never could get any of the contacts merge scripts kindly recommended to me by the #AskFedi #HiveMind to work, but I finally found my own solution, which should hopefully work:

@libreoffice! ;) (and of course @thunderbird)

1. Export contacts from Thunderbird to .csv
2. Make a copy of Contacts.csv for safekeeping, I called mine "Contacts-before-jiggerypokery.csv" ;)
3. Open Contacts.csv in LO Calc
4. Create a key column (A), put "Join" as the label in A1
5. Put =TEXTJOIN(" ^ ",1,C2:AM2) into A2 (You may have to replace AM2 with the end of your row if your CSV export has a different number of columns than mine)
6. Copy that cell and paste it down the entire column A (for every row that contains something)
7. Select A1 only, go to Data | More Filters | Standard Filter...
8. Make sure your A1 field ("Join") is selected, select "Not Empty" for the value, click "> Options" and select "No duplications" on the right
9. Hit Ok
10. Copy everything (now de-duped) to a new sheet, delete the old one
11. Create another new column (B) just to the right of the "Join" column, call it "Repeat?"
12. Paste =IF(TEXTJOIN("",1,C3:D3)=TEXTJOIN("",1,C2:D2),"REPEAT","") into B3
13. Copy B3 and paste it down the entire B column (down to the end of the data)
14. Look where you see REPEAT, and merge the rows that need to be merged
15. Delete Columns A and B (which you added), and save the CSV
16. Delete all of your contacts in Thunderbird, and import the new Contacts.csv
17. Pray
18. Sync your contacts
19. Enjoy!!!

Disclaimer, again: I am still going through my spreadsheet, so I don't know for sure that this works!! XD

#ManageContacts #Contacts #DeDuplication #DeGoogled #UnGoogled #HowTo