Working with map objects without using the editor.

I'll add my question here as it's related to the same issue. I want to customize the hero selection in the map editor, so that when creating a scenario in the game, the desired hero is already displayed in the hero selection window. The problem is that the hero I need is located in the campaign folder of the original game, which doesn't appear in the selection window, just like the campaigns for the Hammers of Fate. Can you suggest a solution?