My attempt at that is:
Code:
({author_sort}{series:| - |}{series_index:o>2s| - | - }{title})
So I believe you would add the following in the Metadata Plugboard
Code:
Format: epub
Device: PRS505
Source Template: ({author_sort}{series:| - |}{series_index:o>2s| - | - }{title})
Destination Field: Title