How to create a custom field and link it to WooCommerce?

Question

Online shopping

Hello. How to create a custom field with its output in a drop-down list, and so that the choice of a value on the product page is somehow noted when it is subsequently added to the cart / checkout page.
Example: I create a product, enter the dimensions in a custom field, on the product page the dimensions are in the drop-down list, when the user selects a size, it is further indicated in the basket.
PS: Yes, I know there are variations, but they don't suit me for some reasons that I couldn't solve. If anyone is interested, I asked the question: WP All Import, how to properly configure price and attribute updates?