How To Create A New Import Layout

We have so far two product export layouts available as model for subsequent importing - one General and one for Variations.

We need a more simple - and specialized - layout for importing a definite type of products that do not need lots of the present fields, but need fields that are not present in the available options. For instance, we don't need category and subcategories, instead, we need the category_id only. The idea being not to allow vendors to chaotically create new categories out of mind, but use the existing ones by simply adding their number.

Hence the precise title of the topic -

How to Add New Fields to the Import Layout