Aktuell gibt es nur diesen Workaround:

This situation is actually handled by Shopify. Shopify does not allow merging customer accounts that have active subscriptions, and it also does not allow changing the email of an account if another account already exists with that email. Unfortunately, this limitation is controlled entirely by Shopify.

I understand your concern. As a workaround, you can:

Cancel the membership that the customer has already purchased.

Since they’ve already paid, create a quick checkout link for that customer using their original email address.

Apply a 100% discount on this checkout so they don’t pay again, and ask them to complete the purchase via this link.

This will ensure that the membership is correctly associated with the customer’s original email.

If you want, I can guide you step-by-step on how to create the quick checkout link for this.

I hope this helps and makes sense.