Do you have any ideas where I can either learn to do it or find a ready made patch
I don't think there's one. I could be wrong, but there's not really need for one either.
I have no idea how the 'Neather acts.
This is because he's been scripted to act in a specific way in every room. This is hidden information and you'll just have to live with it.
If the problem is some of the rooms in KDD:L25 being too hard, you should try the Hints and Solutions board. Having Neather in the editor wouldn't help you with that.