So the first thing to do is to make sure you have the theme api imported
Second: This escape here will display your JSON array for all categories:
{{ categories.all }}
I placed this in the bottom of the layout html. Although I'm sure there are some other spots that would work just fine.
Using that array, loop through it to dynamically create an input box for each category and place it wherever you would like
The next question here, is how you would save and maintain the 'description' or whatever it is you want for that particular category to stay. As I assume you probably want a unique value for each category. Going to be working on just this thing tonight or tomorrow. So I'll check back and update my answer once I've got that part figured out.
On a side note, if your categories aren't going to be changing all the type, you could create just a series of your own variables that match the category and hard-code "write" the value for the text box as it pertains to that category.