In particular, stuff you have submitted and haven't been approved. Would like to know how to do it in general as well though. I would like to add a movie to my completed list but it doesn't exist here.
https://www.themoviedb.org/movie/385871
You will usually get a message from approval staff if your submission is rejected. However if you haven't heard anything that means either they are still processing the submission or simply it has been approved (you won't get message if it's approved so you need to check for yourself on the particular title/people you add)
its not complicated to add a new title,it has basic things you need to add,you can look at the guidelines here but if you go to add title you will see it's pretty straightforward.
https://mydramalist.com/discussions/support/17285-guidelines-editing-and-submitting-new-dramas-movies-and-actors
if for any reason you find it hard to add it,i can do it for you.