Don't have much time, so i can't give you screen shots now(mb later) but i'll try to help you.
1. Create Engineering skill in object editor and customize it as you want(level amount).
2. Create your skill and customize it as you want(non upgrade)
3. Now copy your skill "X" times, where "X" is number of levels of your engineering skill (def 3), and name it (in editor only) "SkillName (UPGRADE LVL 1/2/3)" or as you want to
4. Set statistics of copies to stats that you want in your upgraded skill.
5. Back to your engineering skill, search for (i have polish editor so sry i can't tell you eng name) Statistics - Upgraded Skills or something like that( or just find some other skill names in your engineering stats that will be this
).
6. Change skills (def Cluster Rockets, Pocket Factory, Mecha Goblin(?)) to your own skill.
7. Give your engineering to your hero
Wish i've helped
Sorry for my english