Hey guys!
How to create a option that a customer can fill a customized ‘text’ without any app?
This doesn’t give you a complete how to guide, but does help you with the base html code that would need to be added for those Line Item Properties. Depending on your theme it’s possible you need to modify more than just the html but for the moment you’ve not given a lot of context to work with.
See if this makes some sense:
https://ui-elements-generator.myshopify.com/pages/line-item-property