Hello,
I'm not familiar with web-dev as HTML, WP, etc. Thus using code for manage MB CustomModel is hard and not comfortable for me.
About CustomModel, if I will:
a) Make DB CustomTable by myself via phpMyAdmin.
b) Register a new WP MB CustomModel via code from: https://docs.metabox.io/extensions/mb-custom-table/#custom-models (BTW where this code must be placed?)
Then it will be possible to create (or at least edit) MB CustomFields via your MB VisualBuilder?
(Anyway setup/editing 30-50-100 fields via code is completely terrible!)