Current questions and answers regarding the map editor.

It probably won't display because user-created heroes don't have their own unique ID. And the developers have a reserved list of these IDs somewhere. Simply put, set IsHideInEditor = false in AdvMapHeroShared. Then, in Map Properties => Players => Player Number => ReserveHeroList, add your scripted heroes. It's best to do this for computer-controlled heroes. Then, by setting a trigger (for example, touching a tavern), use:

DeployReserveHero(...);
SetObjectOwner(..., PLAYER_1);

Note: this is necessary if you have reserved the hero for the computer.