Customer Account Accessibility
Shopify has lived a new feature of Account experience. Which has two options available. 1. Classic customer accounts 2. New customer accounts
If you want to show the "Manage Subscription" option in the customer account page then you must need to use the first option of "Classic customer accounts" because this feature has the option to customize the customer account page and we are able to add liquid code in the theme account file.
And the another new option, i.e. New customer accounts, does not provide an option to edit the liquid code and it is totally managed through shopify side so we are unable to add the code & can not add an option of manage subscription through liquid code due to shopify limitation of not allowing access to edit the code.
You will find the option to change account experience option in Shopify Settings >> Checkout and Accounts >> Customer accounts >> Account experience. Please check the below screenshot for reference :-
We have attached a screenshot below and you can also check the differences between both type of account from here :- https://help.shopify.com/en/manual/customers/customer-accounts
If you have any confusion in above and get any queries then feel free to contact our support team at support@webcontrive.com so they are happy to help you and answer your all queries.