Welcome to the forum.
To add items by director:
1. Add the director to People view, and update the record.
2a. I'm not sure what the default behaviour is, so check Preferences - Miscellaneous - Links and note the click behaviour for invisible records.
2b. According to that setting, Click or Ctrl-Click the director's filmography items you're interested in to make them visible in Movie view (they're already there, but this will make them visible). Each click will take you to the movie record, so you'll have to switch back to People view to click the next one.
3. When done, return to Movie view and search for the director. Select the movies and run the plugin.
