Shameless plug:
I created and maintain a tool that automatically synchronizes IMDb watchlist, lists, ratings and history to Trakt based on a custom schedule. The difference from the importer that Trakt offers is that you only need to set it up once and from that point on it will continuously sync things for you.
Check it out here: GitHub - cecobask/imdb-trakt-sync: Automatic sync from IMDb to Trakt (watchlist, lists, ratings and history) using GitHub actions.