It turns out that you can enable debug menu on Google Messages by entering *xyzzy* to the search field. It will add two additional items to the settings menu and a bunch of options to the dropdown menu.
The code phrase could be known to some people as a cheat code from the Road Rush game that was popular in the early 90s.
This menu existed in the app for a long time but recently it was highlighted by Reddit users as a way to fix possible issues with RCS. RCS is a Reach Communication Standard that is here to replace old SMS/MMS. This standard allows Google Messages app to send larger files, stickers, have group chats, and more.
Messages - Apps on Google Play
Meet Messages, Google’s official app for texting (SMS, MMS) and chat (RCS). Message anyone from anywhere with the reliability of texting and the richness of chat. Stay in touch with friends and family, send group texts, and share your favorite pictures, GIFs, emoji, stickers, videos and audio messag…
Source: Reddit
