Basically the title. It's particularly acute for me since (from using different browsers) I have several bookmark collections with a large overlap but no subset relation between them.

The inbuilt settings option "Prevent duplicate links" apparently doesn't resolve this; it probably only works when adding individual links.

In the absence of an inbuilt functionality, one could export all bookmark data (which gives a large JSON file) and operate on it with other tools to remove duplicates automatically or e.g. interactively. Does anyone have a good method for this?

On the BitWarden subreddit, e.g., someone has suggested this procedure, which I may try tomorrow if I find none that is better:

Export all the data as a CSV

Make copy of the file, just in case

Open the copy and do the following: Click Data > Remove Duplicates, and then Under Columns, check or uncheck the columns where you want to remove the duplicates.

Save the CSV

Delete all of your entries in the Bitwarden Vault online.

Import the new duplicate free CSV file

Check if everything looks correct, if it does proceed to delete the first exported CSV and the copy so that none of your passwords are left in plaintext

Done, enjoy