Currently the Slack integration allows filtering integration on folder level. A list level would be improvement, as in we don't (I assume others too) use folder as an abstraction level.
More important than the folder / list (you can create a workaround for that) is what messages get relayed to Slack
I would like there to be a filtering system where I would choose whether I would like to have slack notifs on
  • new issues
  • issues moving state
  • issues arriving to specific state