4 minutes ago, grolulu said:Yes, Classic.
./themes/classic/templates/catalog/_partials/product-customization.tpl
If you are going to use long HTML, you will need to change the length of the field in the database. It now has 255 characters.
Table ps_customization_field_lang field name
ALTER TABLE `ps_customization_field_lang` CHANGE `name` `name` TEXT NOT NULL;