If you don't want to offer a plan anymore, you need to archive the plan completely. Learn more about archiving here.
What is the use case for invisible or hidden plans?
Invisible plans are best used for special promotions: For example, you can offer newsletter subscribers an exclusive plan. A plan can only be purchased if a user has the link to that plan.
How do I make plans invisible?
To hide a plan, edit the plan on the Plans section on the backend by ticking “Hide plan”. Then you can copy the plan’s URL and use it as you wish. (In this case, the plan URL leads directly to the payment process for this plan.)