You can label conversations in a Collaborative Inbox to assign them to a particular category.
To add a label to all conversation:
Click on the message you wish to label
Click on the Label button along the top of the screen
Choose the label to apply, then click on Apply, or click on Create new label to add a new label
Expand the Labels heading on the left-hand side of the screen to show all labels. Click on a label to show only the conversations that have been assigned to that label.
You can remove a label from a conversation by clicking on the X to the right of the label along the top of the message. name.
Click on the Conversations link on the right-hand side of the screen to return to viewing all conversations in the collaborative inbox.