If a conversation is no longer relevant or needed, but you would like to keep it accessible, you can archive it.
Note that if you archive a group conversation and other members are still posting within that conversation, it will be automatically un-archived in your list. You might consider muting a conversation, instead, if you would like to stop getting notifications for it. You'll find the option to mute a conversation in the same place where you select to archive it.
From the web
Click the name of the conversation on the left side of the Messages page to bring it into view.
Click the options button near the top right and you will see options, including the option to archive the conversation.
The conversation will be moved to your archived section, where you can un-archive it, as needed.
If you need to un-archive it again, click the Archived conversations section and choose it from the list.
Click the options button again and you can un-archive it. 👍🏻
From the app
Go to the messages tab and select the conversation you want to archive.
Once the conversation is active, tap the options button (3 dots) at the top right to archive it.
You'll see a popup confirming that you want to archive the conversation.
Once you confirm, you'll jump back to your conversation list and see that the action was completed.
If you want to review your archived conversations or unarchive one, tap the messages header and choose archived conversations.
Tap a conversation to make it active and review the message content.
To unarchive it, tap the options button (3 dots) at the top right.