ML Work Order admins can adjust settings based on the status of the Work Order. Admins can choose whether notes are required when moving the Work Order to a specfic status. 

1. Select Settings > Setup Items > Manage Work Order Status from the left-side navigation menu

2.  Select the Pencil icon () next to one of the Statuses

3.  Check off the Required Notes checkbox and click Save

Now when you attempt to decline a Work Order with the setting enabled this will appear.