Convert group messages to private channels
From Mattermost v9.1, you can change the members of your group conversation by converting the group message to a private channel. When a group message is converted to private, its history and membership are preserved. Membership in a private channel remains as invitation only.
Any member of an existing group message, except guests, can convert that group message to a private channel.
Conversation history will be visible to all channel members.
All group message participants must share at least one team membership.
Select the group message name at the top of the center pane to access the drop-down menu, then select Convert to Private Channel.
Specify the team where the new private channel will be created. You’re prompted to specify a team when all group message members share more than one team membership.
Enter a channel name.
Select Convert to private channel.
Tap the group message you want to convert to a private channel.
Tap the More icon located in the top right corner of the app.
Tap View info.
Tap Convert to a Private Channel.
Enter the private channel name.
Tap Convert to Private Channel to confirm.