Putting series (or other) information into the title field of Calibre is not recommended.
If there is a field for it, that is where it belongs. That way, searches work well.
Save, Send and the Metadata plugboard are where you fudge things to make a DEVICE more usable. The original remains unchanged.
Send to Device and Save to folder, tweak the Filename (used by some bookshelves).
Metadata Plugboard is for Metadata based bookshelves like the Kindle (where the filename is just letters and numbers) that read the internals from the book