Instead of using the advanced search interface once you search, you can directly type "search code" into the search bar. It's really quite cool.
This website has a cool flow chart that explains how to use it:
https://www.labnol.org/internet/twitter-search-tricks/13693/
I'm always curious about the kinds of things people tweeted about before they were hugely successful and this has come in handy for that.
P.S. I wrote a thread on some useful use cases:
This is a really fascinating thing I didn't know about. It's going to make things a bit handier on Twitter for me. I'm always on there trying to find certain tweets from someone or to see which are doing well. Why hasn't Twitter documented this? Is that part true?
I think people generally find the advanced GUI easier to work with but yeah I'm surprised there's not documentation. I like this better because the advanced popup is only available after you search so this is more convenient.
What part are you asking is true?