How to add the ability to add fields directly in the admin panel in OpenCart 3?

Question

opencart

To add one field (input) in the admin panel, for example, on the product page, you need to create a module. I understand it.
(1) But how to make such fields that can be added directly in the admin panel by clicking on the "+" (as in the case of product characteristics)? Those. make it possible to control the number of these fields in the admin panel. I wanted 2 fields - I did 2, I wanted 5 - I did 5.

(2) How to add other types of fields (besides input), for example, select (drop-down list) or radio?