Changing the hero's starting skills.

In the editor (before the game starts, of course). If the hero is already placed on the map, open his properties. If not, but you want to hire him in a tavern, open the "Heroes" tab and click Properties, and then change it as you need.
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Hello, thank you for your answer, sorry for replying after so long. I want to change the basic skill of the Necromancer hero, Vokial (specialization: vampires), from Artillery (ballista) to something else, like defense. And I want this skill to be present in him on generated maps. Can you tell me exactly what the editor is called, where I can make these changes? Will this work if I play with a friend in an online lobby?
Thank you in advance.