--reference

Reference to a replacement key value used to remember an action specific value like issue key, entity id, or similar so it can be referenced later. Each action that allows this parameter will specify that the reference parameter is valid for the action and the first entry listed for available replacement variables help text will be the value set. If you need access to a different replacement variable in your script, you will need to use the setReplacementVariables action after the action to set a new replacement variable of your choosing to one of the other available replacement variables.

reference