Ah, thanks. I got confused because my episode format expression appears to be case insensitive without any flag. I'm guessing this is because I must be using String.match variants there.

I found info about using presets for filtering out paths based on a match here:
https://www.filebot.net/forums/viewtopic.php?p=34979

However, this is not working for me where I have a source folder structure like:
Series Name
--Featurettes
----Season 1
------video1.mkv
----Season 2
------video2 ...