To perform actions on all messages in the thread, such as deleting, archiving, or tagging them:
1.Collapse the thread by clicking ⌄ in the thread line.
2.Select a minimized thread.
3.In the context menu of any of the selected messages, select the desired command, for example, Delete N messages.
You can still perform actions on individual messages by expanding the thread using the > button in the thread bar and selecting the desired message.