Well if the action is made/used correctly it should do what you want:
TITLE: The Trip To The Naboo Temple And The Audience With Boss Nass
afterwards:
TITLE: The Trip to the Naboo Temple and the Audience with Boss Nass
Action type: Replace with regular expressions
Field: _TAG
Regular expression: \s(a|the|of|to|an|and|with)(?=\s)
Replace matches with: $lower($0)
You put your "small words" into the brackets seperated by |
The \s stuff makes sure the words are only lowered if preceeded and followed by a space.