You will need to install a user script manager extension to install this script.
UPDATE (3.0.1): Thanks to monk-time the script now works on Chrome without having to modify the source code!
Inserts a small input box after a list in editing mode. IMDb IDs will be automatically added to the list. If you input titles the search is automatic but you must select the correct title manually. Regular expressions are supported.
To import ratings:
Make sure the format is: rating,imdb id/title