Current questions and answers regarding the map editor.

so that the enemy hero, after losing a battle, always reappears in their city.

There are 2 options.
1) Force him to reliably reappear in the tavern after defeat. See the MakeHeroReturnToTavernAfterDeath function.
2) Place the hero in reserve and create a trigger for his loss. At the beginning of the game, and after each of his losses, deploy him (see DeployReserveHero) to a specific location on the map.