Can you make the search filter more powerful by enabling boards to be filtered by the colour of the stickie note. Take a look at the way trello enable cards to be filtered by label / person, it’s this kind of thing.
why? myself and colleagues use colour coding to indicate grouping of various kinds. e.g. a collaborative board where each person was assigned a specific colour stickie note. a simple filter would enable analysis / views of the data gathered much more easily.