Been answered (sorta) many times because the All solution is ugly DB structure wise.
I have a custom series like column That is for the single Alternate.
I also use Hierarchical series: Pern.Dragonriders and ONLY Number on the sub series. Nobody is going to arrest you for changing how you enter series names

(and you must since publishers (and Authors) are not consistent or change their min mid series. There are those cases where an Author started with a plan and the series took over

Roll with it and adapt)
And for Anthologies or Boxed collections

{Series} is "Various" and the {AltSeries} is the top runner (or my fav) out of the lot.
Although if you really must have precision: EPUB split (and archive the master)