I added a custom column (#subtitle)
When it comes in AS part of a title, I split it to there. (or I may see it on the cover and add it by hand)
If the series name comes in, I split that off also.
You want clean metadata, be prepared for some effort
Calibre has tools to help with repetitive tasks:
Saved Search and Replace
But almost every ADD gets some tLC (not always tender
) metadata editing