I'm on a mobile device right now so I can't look at the CS, but is there a way to edit all creature leveled lists within a region in one step? I'm thinking of making a mod that creates localized ecosystems, so for instance you would see durzog in Blackwood instead of wolves, winterized Spriggans in the Jerall mountains, or tigers in the Colovian Highlands versus panthers in the Great Forest. I'm basically curious if there's a quicker way to do this than editing each leveled list by hand.

If I read you right, you want a way to replace list A with list B in a region, rather than open up the list and make changes to it. I don't think search and replace has region as one of its scope options, but it will do it for a whole cell at a time, which reduces the effort by a factor.

You wouldn't want to edit the list, as that would affect it in all regions. Creating a new restricted list for each region also avoids the rule-of-one problem of another mod putting it all back the way it was.