The current filtering capabilities in data views are powerful, but there are some restrictive details. For instance you cannot combine filters of the same type, and there's no way to modify the operator between filters.

In other words you could not filter the Posts data view to show posts where:

Category is: category X, and any of: category Y, category Z, or Tag is: Tag X, and Tag is not: Tax Y, Tag Z.

How might we extend the filter UX to cater to such options?

One idea would be to provide an "Advanced filter" option in the Add filter menu. It would add a filter chip like any other, but the configuration popover would be more comprehensive. Here's a very rough mockup to demonstrate the idea: