Current questions and answers regarding the map editor.

Here are the questions:
1. Can existing maps be modified?
2. If creating maps with an underground, how do you transition from the surface to the underground?
3. How do you create maps like Campaigns/Scenarios?
4. How do you create a portal link (entrance) and exit? I made a bunch of them, and the idea was that a hero entering one should teleport to the castle, but it doesn't work at all, and they end up somewhere else. What should I do?

1. File/Open/ select the desired map and modify it.
2. View/Show Underground
3. This is a rather lengthy process, involving a lot of work with scripts, etc. I advise you to communicate with people on the forum of this site: http://all4heroes.net, there are many experienced map makers there.
4. Select a portal, press the spacebar, set the Groups, the same numbers on 2 different portals mean they are linked (that's how it should work, I've never checked it myself :) )

Added after 7 minutes

I have a question: how do you create lighting in the underground, and how do you take a screenshot?

I don't know about the lighting, but there is a button on the control panel called Make Screenshot, which is used to take screenshots.