(Request by Pratik Solanki)
There are several ways this could work:
Probably the best way is to click on the previews and then quickly type the number. If you press 1 and then quickly after press 2, it would be 12. But I have no idea how to implement this in Blender (simple or complicated).
A simple input box underneath the previews where you can type a number.
A search box like for materials dropdown. Best to have this in previews, but I don't think that's possible at the moment. Other option would be to have an extra dropdown list underneath the previews... but then the UI gets rather messy.
(Request by Pratik Solanki) There are several ways this could work: