Block Nickel from indexing sdcard on start-up?

I'm using a Kobo H2O 1st edition with NickelMenu, basically for the purpose of running Koreader on it. This is generally fine, but when I haven't used it for a while and it shuts down, on rebooting it takes about 10-15 minutes before I can get into Koreader because Nickel is doing something, I assume (re)indexing. I assume it's so long because I have a 128gb sdcard with a bunch of things on it.

Is there a way to block Nickel from trying to index things, at least on the sdcard?