Questions about the Heroes 4 map editor.

In cities of different factions, the selection of heroes in the Tavern varies. For example, in Chaos cities, you cannot hire heroes from Haven, Sylvan, or Castle. 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. Perhaps it's impossible to change this in the Editor at all?