Pin a conversation in Messages on Mac
With macOS 11 or later, you can pin specific conversations to the top of the Messages list, such as the people you contact most.
In the Messages app on your Mac, select a conversation.
Do any of the following:
Drag the conversation to the top of the sidebar.
Control-click the conversation, then choose Pin [name]. Or if you have a trackpad or a Magic Mouse, you can also swipe right with two fingers on the conversation in the sidebar, then click the Pin button .
To unpin a conversation, drag it out of the section or Control-click it, then choose Unpin.
If you receive content that is especially interesting and Shared with You is turned on, you can quickly pin it in Messages and it will be elevated in Shared with You, Messages search and the Details view of the conversation. See Pin shared content.