I think it must be 4 small buttons(16px height) below the search field, with icons (all, actors, actors logic, scene logic) or without it. So, when we are typed search letters by default it searching in all and hover button "all" and than we can use keyboard arrow buttons "left", "right" to shift between search buttons and activate this buttons with enter press or without. Anyway this is almost impossible to use Stencylworks without the mouse, but searching by categories allows us to not go back to game center each time when we need to open some resource. work will be faster.