(EDIT: This is a feature request, not a question, but I made a mistake and cannot change the icon from blue question mark to yellow light bulb.)
One neat little feature in RTM and their "smart lists" (i.e their saved searches, or "custom views" as I prefer to call them) is:
The capability to specify in the smart list's selection critera that you want to include or exclude any tasks that are identified by some other particular smart list's selection criteria. This is useful when you have many lists with complex criteria, and wish to avoid unnecessary repetition.
Let's say you have made a saved search with half a page of selection criteria. And you want to keep this as it is, because you are going to be using this often. Then you realize that you also need something quite similar. Then, obviously, it would be very handy to be able to specify in Toodledo, in the Search criteria:
Saved Search | is | NameOfMyPreviousList
any criteria for widening the selection
any criteria for narrowing down the selection