Gmail on the web has got some neat tricks to make emailing a bit less tedious, but these features can take a while to reach the mobile app. Support for @ mentions was added to Gmail back in 2018, but it’s only now that the feature is landing on Gmail for Android. Still, not everyone will get to use it, at least for now.
In the email body, you can start typing your contact’s name after “+” or “@” to see a list of matching people, as shown in the included screenshot. Tap on the one you want, and you’ll see a hyperlinked mention of them in the text area. These tagged names will also be added as email recipients. Removing any of these mentions from the body will also delete the corresponding contacts from the “To” line above.
This neat shortcut is currently available only for G Suite customers, leaving out the personal Gmail account holders for now. It should reach all eligible users around mid-September.