Adding new professions isn’t that hard and the rules are pretty simple to figure out, just look at the JSON descriptions of similar professions for a good example on what they should look like. Reading the part in JSON_INFO.md about professions also provides lots of information if you want to be sure how everything works.
Also, while it doesn’t cover adding new professions the guide by mlangsdorf is a good place to start if you aren’t already familiar with JSON but wan’t to get into modding (or adding content to the core game).