I have a second (custom column) series field for when the main can not be made to work for me (OR the Author renamed a series. That column gets the other name so searches have a chance

)
Just be prepared to manage by hand as metadata sources are the wild west in lack of consistency. We are talking, even the SAME source, same series )
Hierarchical is my main method
I frequently rename series to fit my methods: (be prepared for disappointment when that can't cope with deep nested sub series )
(

Manage Series Plugin can be of a great help with the Regular Series column allows a uniform naming on the selected books and renumbering. )
(mostly) By Universe: (books with a set foundation: place, people, premise)
Pern.Harper Hall
Solar Clipper.Golden Age
Spinoffs: (many, many spinoffs of the original, where a character got their own series) This is where I frequently use the second series column
Spinoff name gets {series[index]}, Base series gets put into here with its name and index in the overall)
Calibre only supports 1 index per field.
And the Elephant in the Library

Anthologies with multiple different series. (IMHO Column count bloat is not a desired solution)

EPUB Split
<Various [0]> is the Main, (Pick your Fav outa the lot ) for the second column