The simple answer is to remove them from the database. But that requires a backup and down-time.
You could write a plugin (or use the script runner plugin, I think) to remove them with a bit of coding.
It's mostly harmless to do this, but it makes a bit of a nonesense of the history, because you can suddenly have issues with no record of their old workflow. It's rather odd to see records like "on Tuesday, it changed from Open to In-Progress", open up the workflow and find out the current one doesn't actually have Open or In-Progress. A spot of explaining to users is needed there...
Connect with like-minded Atlassian users at free events near you!Find a group
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no AUG chapters near you at the moment.Start an AUG
We're bringing product updates and pro tips on teamwork to ten cities around the world.Save your spot