The UI for categorisation on Commons has a very nice feature that next to categories there is a down-arrow link, that when clicked presents sub-categories of the current category for narrower categorisation, and an up-arrow link that when clicked offers super-categories -- allowing the category tree to be explored efficiently and quickly to find the most appropriate choice.

It would be valuable if Wikidata could offer something similar, for statements with values that live in a strong hierarchy -- for example P 131 "located in the administrative territorial entity", with values in the territorial entity subtree; or for P 31 "instance of". with values in the sub-class tree -- to make it similarly easy for such statements to be refined (or made less specific), presenting the user with a set of available refinements at a click.