Change Invoice Text Description without Needing an Amendment to a Product
If you want to amend what goes in the invoice text on the product summary screen in an active subscription, you need to create an amendment to the product to make this field editable. This does not seem like it should require a full on amendment to a product to just change what appears on the invoice text. (If you look at the options for reasons why you are even creating an amendment, none of them fit 'to change the invoice text field'.)
My recommendation is just to make that field editable and have it change on the billing summary without needing to create an amendment and generate the billing schedule again. Or just a way to make that an easier process that does not require an amendment.