Can't select specific field to copy when two fields have the same name.

Overview:

In some scenarios, if you have custom fields with the same name, then you have to use the ID of the custom field in the post function.

Instructions

Follow the below steps to update the post function with the custom field ID. 

1. Log in as a Jira Administrator and Click on Cogwheel → Issues → Fields under Custom fields. 
2. Navigate to the desired custom field and on the cogwheel → Configure. 

        3. You will be able to see the custom field ID in the address bar as shown in the following screen.

         4. Take a note of the custom field ID's and navigate to the Workflow associated with the project. 

         5.  Select the Post functions tab

         6. Copy the Custom fields Id and enter in the post functions as shown below

           7. Following is the screenshot of the post function after you save.