Questions about the Heroes 4 map editor.

In cities of different races, the selection of heroes in the Tavern varies. For example, in Chaos cities, you cannot hire heroes of the Haven, Sylvan, or Castle factions. I can't find where this is specified in the Map Editor – which races are available for hiring and which are not? I only found a tab for selecting available heroes, but that's not it; it doesn't affect the taverns. Maybe it's impossible to change this in the Editor at all?