Default activated categories for all users is again a bad design. If the category always has to be active, the fields should have been added to the main table. Unless the security of the fields is different compared to the main table.
Anyway, if you switch to use "forms" to display the content of categories instead of the classical (2012) fixed position layout, you can control serverside the display of fields in the FormFieldsEditCustom.txt.
There are many steps to take, too much to document quickly