To add a new skill with HL Editor is fairly straightforward if you are adding them as additional skills, the only thing easier were the languages. Adding Occupations is more difficult but not insurmountable in most cases.
There are some videos from Lone Wolf showing how to do it. Below is a link to You Tube Videos for Realm Works and Hero Lab.
https://www.youtube.com/playlist?lis...wvP8zs_qVSrzoM
I only started playing with the editor for Cthulhu a week or so ago and I've added 84 Occupations, 13 Skills, 1 Spell and 2 languages. Most were from the Investigators Handbook although the spell, languages and one Occupation were home brew. The major issue that I have found is with adding a few Occupations that have more than 2 sets of choices for occupations that can't be mixed. I think it may need some changes that I'm not confident to try to add , and not sure if I can.
Let me know if I can help. If you let me know exactly what you want adding, I might be able to let you have a bespoke file with them in.