Linking existing WP user accounts

We currently have a WP (buddypress) site with manually approved users. The Patreon plugin seemed IDEAL, as this would save us a lot of admin hassle.
However, when our users log in using patreon, it creates a new account for them. How do we merge the two accounts so that our patrons still have their existing profile data/loyalty points/forum history in tact?

If your users are logged in to your WP site before they log in with Patreon, the plugin will link the two accounts from that point on.

If a user is not logged in to your WP site before logging in with Patreon, a new account will be created for him/her, and will be linked to that Patreon.

And what if somebody has created a second account with Login with Patreon accidentally. E.g. There was an account of this person prior to logging in with Patreon. Is there a way to merge these duplicates?

The user can log out of Patreon and WordPress, then log in with his/her original WordPress account, then log in or unlock via Patreon to link that account instead.