Similar to changes in the document, SMASHDOCs also notifies you in the case of new contributions to a conversation. If there are new comments/questions or answers, that you have not seen yet, a red notification appears on the left side.
Click on the respective conversation tab to see the list of all conversations that contain updates. Choose a conversation from the list, and you can see its course. If needed, you can reply and/or mark the conversation as complete.
In order to mark the new contributions as read, just go back in the list of conversations or click on the "Mark as read" button.