The approach I've used for years is to create a collection for each series.
I use
series as one of my columns in the device driver to create a collection per series. Additionally I use a metadata plugboard to set the book's title ob my Kobo;
Code:
Format: ePub
Device: KOBOTOUCH
Source Template: {series:re(([^\s])[^\s]+(\s|$),\1)}{series_index:0>2s| - | - }{title}
Destination Field: title
This makes finding books in series very easy for me.
I can just sort by title and see all books in a series in the correct order.
I should add that the plugboard prepends an abbreviated version of the Series and the series-index to the books title; so for instance
Harry Potter and the Philosopher's Stone appears on my Kobo in the collection
Harry Potter, with the title
HP - 01 - Harry Potter and the Philosopher's Stone.