Hi @Not Now ,
You could try following things to delete your old favorites.
1.please navigate to the edge://settings/profiles/sync
and turn off the sync favorites.
2.Go to edge://favorites
(or pressing Ctrl + Shift + O) and click Deleted favorites on left panel.
If there have any stored deleted favorites items, you could right-click (or select and hold) the item and select delete permanently.
3.Clear your browsing data.
Settings> Privacy and services> Under the “Clear browsing data” section, click the Choose what to clear button>
Check the boxes "Browsing history, Cookies and saved website data" and "All data from the previous version of Microsoft Edge" etc. and click on Clear now.
4.Try to re-export and import favorites and check if the issue persists.
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Best Regards,
Wenying Lu