If we need to view quickly a lot of tag combinations with some tags common for each combination (A+B-Z+C, A+B-Z+D, A+B-Z+N-P, A+B-Z+X), it would be helpful to pin common tag combination (A+B-Z) once, "pin" it and then sequentially pick individual ones (+C, +D, +N-P, +X) by just single click on each one.
It also would be perfect to have an ability to save pinned combinations (something like "Save search criteria")
Another reason - some notes are private, an should be hidden by default to prevent accidental expose to other people who see display. We could do it by pinning notes related to tag "personal" as
boolean negative by pressing [Alt].
Customer support service by UserEcho