Not all processes or workflows can be kicked-off automatically. Sometimes you want to manually trigger a rule to perform a task, or to test your rule. You can achieve that with the Manual trigger.
This trigger adds the ability to manually kick-off a rule from your Jira 'view issue' page. You also have the option to restrict which groups can view this trigger.
The manual triggers appear in the "More" dropdown on the issue.
Once the rule has completed a message will appear saying whether the rule ran successfully or not. The issue content doesn't refresh automatically - a manual reload is required.