Do you already have 10,000 titles on that list? Or are you using the add box on the Edit List screen and the search doesn't find it by name? Short subjects and tv episodes have that problem. I can add it to Watchlist or a custom list from the title page using the + button. Or on the List's Edit page using the title constant tt0020530. https://www.imdb.com/title/tt0020530/
