As per reports, Google is testing pinned conversations in Google Messages since the last year. This feature was previously present in other messaging apps. This feature allows you to pin a favorite contact at the top for easy access.
Google had improved its messaging with features like end-to-end encryption, starred messages, and more. And is dedicated to improving it day by day. They have introduced RCS which has been very well received and works in many countries.
Google officially added starred messages in G Messages a few days ago. As per reports by XDA Developers, some users were able to pin messages by holding the chat thread and clicking on the pin option which appeared magically. After pinned, The chat remains at the top of the inbox. But this is only been spotted on some devices with the 8.3.026 beta update of G Messages, which will only work on Android 11 and 12.