It would be fantastic if the custom dashboards could provide data for a different range. For example, you want to look at inbox placement for December and January. You need to create two dashboards, change the date range, and screenshot the results; if we could individually set the date range for each widget - great success!
I've also submitted this as a feature request in the past. If this is something that would help you and your team with reporting - consider submitting it as a request 🙂