Can I Limit the Products Added to Existing Bold Subscriptions
How can I limit the number of products a customer can add to their existing subscription in Bold Subscriptions?
If you have enabled the Customer can add products to their existing subscriptions setting, customers will be able to add any amount of products to their existing subscriptions. There isn't a feature to limit the number of products a customer can add.
If you do not want subscribers to add products to their existing subscriptions at all, you can disable this setting in Settings > Customer portal.