I'm encountering some strange problem: when I check Knights.esp as a background file (non-active) and try to save - no matter does I've done something or not - CS crashes. There are few seconds of silence and after that, I see this delightful message "Program has made an improper operation...". Do you have an idea what causes this problem? It's a bit problematic, since I wish to do some KotN-based mod and I can't do that with this.

I've changed the modification date for Knights.esp file to 2008, since it was 2100 before, and it hasn't helped. This was my only idea about the reason of crashing...

You can't create an ESP with another ESP loaded. Even if it's not the "active" file.

You'll have to try some tricks, like "ESP mastering" (search for it), or using TES4Edit if you want to make a mod that is dependent on Knights.esp

That's strange, because when I've been creating my "Two-Handed Dragonsword" mod, I haven't encountered the same problem with DLCBattlehornCastle.esp.

Well, I'll check those solutions you've mentioned. Thank you.