@david, this is excellent and looks like a great fit for a use case I have.
A couple of things… (you knew that was coming, right?).
I moved an untagged item to a tagged column and the confirmatory modal seems to contain some placeholder or string interpolation text.
Secondly, I’d love to see the ability to restrict the cards that are displayed across the columns to only open topics (i.e. not closed or archived). Right now, it appears that all topics in the column that match the category or tag are displayed.
Perhaps a theme setting that asks “Only open topics?”
Great work!