How to fill Due Date field with a custom field value using Create on Transition app

This article gives step by step instructions on how to copy the value of Next Due Date custom field into the Due Date field by using the Create on Transition app.

Instructions

For example, following is a custom field called "next due date"(custom field type is date) and its value is set to 18/Dec/19.

Here are the steps to follow to update the post function in a workflow and copy the "next due date" value into the due date field:

1. Log in as an Administrator into your Jira instance.
2. Select Projects from menu bar and click on the project name. If the project is not visible from the drop-down, click on  View all projects and select the relevant project.
   
3. Click on the Project settings in the project page to administer the project:
   
4. Go to workflows section and click on the pencil icon adjacent to the relevant workflow scheme:
   
5.  Click on the transition, that has the Post Function to be updated. For example, Done is the Post Function
   in the below screenshot:
   
6. Click on Post Functions and then click on the pencil icon.
   

7. Click on Detailed Fields and then set the substitution variable %original_customfield_10300% in the Due date field. As such, when you click on the Done status in the Jira issue, the value of the next due date is copied into the Due date custom field.
   

8. Please follow the below steps to get the next due date custom field ID:
      1. Log in as an Administrator in your Jira instance.
      2. Click on Issues from the dropdown list
           
         3.  Go to Issues from the top menu bar and click on Custom Fields
             
          4. Search for the next due date custom field and click on Cogwheel() to the right of it and then click on Configure button.
              
           5. Custom Field ID is shown as customFieldId from the URL.