To add the 'Copy value from field to field' post-function to a transition:
Click Edit for the workflow that has the transition you wish to configure the post-function on.
In the Workflow Designer, select the transition.
Click on Post Functions in the properties panel.
Click on Addpost function.
Select Copy value from field to field from the list of post-functions.
Click on Add to add the post-function on the transition.
Select the field name from the Source Field drop-down.
Select the field name from the Destination Field drop-down.
Select the options provided to add the required parameters.
Click on Add to add the post-function to the transition.
Note that you should publish the workflow
When you add this post-function to a transition and trigger the transition, the add-on copies the value(s) of the selected Source Field to the Destination Field of the current issue.
Use value before current transition
Takes the selected Source Field value as it was before the transition. This is useful in a case where the user modifies the source field on the Transition screen during the transition and you need the field value prior the modification.
Return "parent-child" for cascading custom fields
This option is applicable for Select list (cascading) custom fields. If you select the Return "parent-child" for cascading custom fields option, values from both the parent and child lists are copied into the destination field.
For example, a custom cascading field has the values A and 1 in the parent and its child lists respectively. When this field is copied into a text field
without the option, the value 1 is copied into the text field
with the option, the value A-1 is copied into the text field.
Ignore empty values
Will not set (clear) the destination field of the current issue, if the value of the source field is empty or null.
Add source value(s) to destination field
Appends the value(s) of the selected Source Field to the Destination Field of the current issue. This is applicable only to multi-valued fields.
Create missing value(s)
Allows automatically creating any missing value(s) while copying values that do not apply to the destination field and hence should be created from the source field. This is applicable only to Affects Version/s, Fix Version/s, Single version and Multi-version picker type custom fields, Components, Radio buttons, Checkboxes, Single select and Multi-select list type custom fields.
By default, all errors (Java Exceptions) raised by this post-function, including those raised by custom Groovy scripts, will be logged in the JIRA log file but will not be reported to the user and will not prevent the transition from completing. However, when designing new workflows or troubleshooting them, it is more convenient to be notified immediately of any such error during the execution of the transition. For example on the production Jira instances you might want to show errors only for the post-function(s) being worked on, in order to avoid disrupting other workflows. To make errors raised by the current post-function prevent the transition from completing and show the error in the browser, select Make transition fail when an error occurs in this post-function.
If you want to show all the errors, either only to the admins or to all users, configure the option globally on the JMWE configuration page. For example, on development and staging Jira instances, you can activate error reporting for all JMWE post-functions, to display all the errors and it is recommended to do so, and on production Jira instances you might want to activate error reporting only to administrators so that they can be made aware of configuration errors.