Actually, we have a relevant topic: Walkthrough for custom maps, where we discuss various issues related to this. You didn't find the tent in the editor? Seriously? How did you search? Didn't the "Edit - Find..." menu help? I found it at cell 26,16,0. If you couldn't find the map editor itself in the game, then it's the file h3maped.exe. It's convenient to create a shortcut to it on your desktop. There is another very useful tool for completing single-player maps: ProspectorRT. It will find everything that cannot be found using standard methods, including spells and artifacts in events, with monsters, etc.