Here's a youtube playlist of over 1.400 secrets in official worlds and add-ons: https://www.youtube.com/playlist?list=PL4Titri5DZfy89qXl83C12Nx4A58Le46E You can dig in there to find the secret you're looking for, I think it's exhaustive for official worlds. Some of the secrets in official worlds that are shown in here are done in 040, but they are all the same in 051.

Happy digging!