Summary

 Copy parent value of cascading field to another custom field

Environment

Jira Cloud 

Solution

Using Automation for Jira to achieve this : 

Step 1 : Go to Jira settings -> System -> Automation rules -> click on create rule

Step 2 : Choose the trigger -> field value changed -> choose the field (cascading field)

Step 3 : Next choose the action ->

• edit issues
• choose the field
• add the specified smart value as per the screenshot.
  
   Note : The value specified by us on the smart value is based on the customfield ID for the cascading field that we have. It is unique for each field.
   You can retrieve the customfield value from Jira settings -> Issues -> custom fields -> search the field -> click on the 3 dots to your right -> click on "Edit details" -> in the URL you can see the ID]
  
  

{{triggerissue.fields.customfield_ID.value}}

Step 4 : Once done, publish the rule.