Thanks man , did you previously make a mountains ?
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This is written in the manual (You can download it on the modification page). But there is no video, because this is a new entity (CustomEnemyCollision) from the mod. It's unlikely that anyone made a new video about this. There should already be some kind of guide about all old entities.
I highly recommend joining the SeriousSite discord. Then the community will be able to help with questions more quickly. There are some English-speaking users there and they can also be helped with questions. No need to be shy)
There may be a problem in the EarthSculptor program itself. I had problems with the program until I updated the drivers for the video card. But my problem is different from yours, so this probably won't be the solution.
The author of this video is CR!STALLL. He is in our SeriousSite discord. Most likely he will be able to help you. Besides, there are other people there who may know about your problem. Ask a question in the development channel.
When I talked about the author, I meant the author of the previous video about terrain. Just find a person with the nickname CR!STALLL. Write to him in our SeriousSite discord or just on the development channel. In fact, it's quite tedious to help here. It's much better to ask these kinds of questions in the community. It is unlikely that the problem will be in the video card, but perhaps they will find another problem that can be solved.