I don't really have a trick, but a question. In HOMM3, if you didn't like the skills offered, you could reload from a save, gain experience somewhere else on a different day, and different skills would be offered. In the fifth game, this didn't work. Is it possible?
As far as I know, no. You have to replay the entire scenario from the beginning, then different skills will appear.
By the way, as far as I remember, in the 3rd game it was the same, wasn't it?