AppForest Prevent Duplicate Purchases of WooCommerce Membership
This is an addon that prevents users from purchasing multiple WooCommerce memberships.
Here are two membership-linked products and two regular products. The currently logged in user is already subscribed to a 12-month membership.
Therefore, regular products can be placed in the shopping cart and paid, but subscription products are blocked from purchasing.
If you go to the detail page of the subscription product, you can see that the purchase is still blocked as the number of remaining membership days is displayed in the gui.