I use Areas to separate Work items from the rest of my life, but in some cases there is overlap. One way this happens is in my Notebook “Things to Buy” which can contain work and non-work items
Currently, the Notebook itself uses tags and thus will only display in the sidebar if the tags match the Area (i.e if I have no tags on the Notebook, it will not display in the sidebar when I am in the “Work” Area). It would be much nicer if the Notebook displayed in the side bar if any items in the Notebook matched the current Area. In other words, filtering the items in the Notebook, rather than the Notebook itself (but hiding the Notebook if no items match the filter)
I could, of course, solve this by having two or more Notebook, one per area, but that feels very clunky, especially if you have many areas.