It's actually really easy
void OnStart()
{
SetEntityPlayerInteractCallback("hatch", "ChangeLevel", true); //Adds a callback to call the function ChangeLevel when "hatch" is interacted with. True simply means that the callback is only called once.
}
void ChangeLevel(string &in entity, string &in type)
{
ChangeMap("01.map", "PlayerStartArea_1", "", ""); //Changes to level "01.map" and you will start at "PlayerStartArea_1", of course change that if you wish.
}
//This is a comment explaining what each line does, and is ignored by the engine