I actually thought about the card thing but it was going to take too long to put together. Proto REPL already has a way to do the extension thing

You can write an extension that can display things in any way you want. It's not exactly what you're talking about but it can accomplish the same thing

Proto REPL charts Clojure functions just return data like this:

[:proto-repl-code-execution-extension "proto-repl-charts" {:type "chart" :name name :data chart-config}]

The extension gets called within Atom to do the displaying https://github.com/jasongilman/proto-repl-charts/blob/master/lib/proto-repl-charts.coffee#L28

is there a way to rerun the last command sent to the repl?