Recently my team and I started utilizing the Inbox functionality in order to facilitate a specific workflow for one of our projects. An interesting idea that we came up with is the concept of Multiple Inboxes. This would allow a user to filter through multiple types of surveys that might need to be reviewed. For example, if a field crew is reliant upon a Remote Inspector to review their surveys and provide feedback or comments, the Inbox could function as a means of filtering the different types of review results (i.e. Passed, Failed, Pending, Incomplete etc.). So instead of having one Inbox for your survey that has an expression set to Failed surveys, you could have multiple Inboxes representing the various types of surveys you would want your user to be able to filter by (Passed Inbox, Failed Inbox, Pending Inbox, Incomplete Inbox).
Please feel free to contact me if you have any follow up questions. I feel like this functionality would be something that others would really appreciate as well.