When selecting a filter in the sidebar, it should filter down the current view as opposed to changing it to only showing that tag. For example, if I have a Folder called "Case Studies" selected, and have a tag called "final," if I click the final tag, it filters to only show #final tagged items in the Case studies folder. I would then be able to select multiple tags to turn them on/off for filtering. Selecting a different folder would keep those tags engaged and change the folder view.