As an admin, I want to be able to select a vocabulary in the Category Facet widget
Make it instance-able and allow the user to select which Vocabulary to show, it's pretty much unusable for Commerce right now)
A proposed solution is to allow the Category Facet widget to either be scoped to a vocabulary or not. If it's scoped to a vocabulary, then the user selects exactly one vocabulary to scope it to.
Benjamin Turner has implemented some widget templates to achieve a vocabulary grouping or displaying the categories of only one vocabulary, see: