I do close to the same as David, except i set series (preferences:Look &Feel:Hierarchy (a tab)) to hierarchical (note: the Tag browser gains an arrow and if you click the top level 2 times, you get double + and ALL children show.)
Valdemar.Mage wars
Now it gets dicey

Sometimes I number from 1 if it is a spinoff/cycle
AND
I also use my {#altSeries} to place it in Valdemar
ALSO (

Authors!

) I turn the flat-filed Series groups from Fantastic Fiction (my primary source) into hierarchical when it appears the series is just more / another cycle
eg. Universe.cycle (my Valdemar has 14 children cycles, some probably should go to level 3