See also the official documentation:
You must have permissions to do this - e.g. be an owner or moderator.
Go to Messages on your group home page.
In Messages, change to Topic View using the dropdown menu.
An arrow with a dropdown menu appears just on the bottom right on the signature and date line.
There are links to these functions:
- Close Topic - this function closes a specific thread. In Settings, you can set up a default date for threads to close, but this link allows you to close the specific topic.
- Edit Subject - includes adding a tag
- Make Sticky - this topic would always appear first on your group site. You can also "unstick" a post.
- Start Merge - to merge topics or threads - see Merge instructions
- Delete Topic