I attempted to use the "Manage Series device in device library" to temporarily overwrite it with the reading list order, used order series shelves, and then restored the original series from Calibre. It didn't work.
It'd probably be a bit of work to do every time I updated my reading lists too.
EDIT: I found some older posts mentioning that the series sort thing was broken in newer firmware. Is it still broken? I guess I could mess around with title plugboards or something.