Would it be possible that when the Slack workflow item sends a message on successful build, it also pins that message? In my successful build message I send the public app URL to the channel. It’d be fantastic if the pinned items list on the right would always have a link to the latest build of the app!
I’m not sure if this is possible through Slack’s API.
If you can find anything related in the webhook/messages API (basic message API / attachments API) let us know, or send a Pull Request into the Slack message step’s repo 
Well, if you can figure out how this could be integrated into the Slack step, we’d be happy to review & accept the Pull Request
Or of course feel free to create a #feature-requests