Subscription Switching with Existing Simple Subscription Product

My client has a single product that has been a simple bi-monthly subscription for years. Now she has added a yearly subscription for this one product. A few months ago I added a new simple subscription product with a Yearly option.

Now she wants to give her existing customers the option to switch to the yearly subscription or new yearly subscribers the ability to switch to bi-monthly.

I did find this article on how to set Subscription Switching up https://woocommerce.com/document/subscriptions/switching-guide/ but it does not seem to cover how to group existing products so the customer can change plans in their “My Account” page. Is this possible or will I need to create a new variable or simple products and then group them?

If I have to do the new products and remove the old ones will this break any of the current subscriptions?

Thank you!

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