The order is the same as you clicked manually, to get what you want
This tweak only applies on startup.
You must be lucky. Many series that I read have different authors. Tossing an Author sort in after a series sort makes a hash of the list.
If you are interested in a Series, Author...
use the Tag Browser. Sort the results as you go
(Series, I usually want to see in Series_indexed ORDER)
Non-series, I might want to see an Authors work in Title ORDER
The thing I am trying to convey is that Tags work WITH sort. Neither is a good replacement for the other