Questions about the Heroes 4 map editor.

If randomness is planned, then the player has a "save/load" option as a fallback.

Sure. In my opinion, saving after every step is an even greater form of masochism... The goal is not to kill the player, but to annoy them :D

"Hostility" can be implemented, for example, by strengthening the neutral creatures.
Or by making passages toll roads.

In that case, you need to somehow explain to yourself and others why everything is the way it is, and not otherwise. If the neutral creatures are strong and numerous, then where did they all come from, and what are they doing in this dangerous place? If the passage is a toll road, then who on earth could have thought that anyone would even consider going there, and be willing to pay for it? And also, why can't I level a small, lonely tower to the ground, even though I can easily deal with a pack of black dragons? And if the guard is serious, then again, what could they possibly be guarding?! But here, everything is simple and logical - it's cold and empty, and an imprudent traveler will quickly perish in such a place without any outside help. But, firstly, you can prepare accordingly, and then it will be easier, and secondly, you can simply not go there; the map provides at least two other possible routes.