If you're already putting your own frontend on it in Slack, you could add a 're-run' button to that failure notification that hits the API for that? (I assume there is one.)

There's a weird DSL for buttons/layout in Slack, but it works, and obviously it's pretty easily testable, just fire the examples at your own endpoint and tweak it until it does what you want.

My own main frustration with Actions is just that the docs are bad, making it hard to configure.