Username Auto-Completion (iOS and macOS
How do I get Twitterrific to auto-complete usernames when I write an @ Reply?
For an @ Reply, type the "@" symbol in the compose window, then begin typing either the username or the real name of the person you want to mention. Twitterrific will display a list of matching names for you to choose from. On iOS you can simply press the space bar to quickly use the top autocompletion suggestion. On the Mac, press the Tab key to select the top hit and continue composing your tweet.