How to display custom fields, activity types and catgories in case manager

Hi, community.

I have custom activity types besides the factory ones (Call, Email, etc):

But in the case manager of sections, when trying to set up activities tied to the stages, I can only see these:

Why can't I see my other activity types?

And also, how can I add the activity category field to this view? Or any other field, for that matter? Which schema must I modify and how?

Thank you!