Make Parent Link mandatory in workitem
One answer
There is no built in capability to do that. This would require creating a custom advisor/precondition for work item save, that checks if there is a parent and prevents saving if there is no parent. This blog post shows an advisor: https://rsjazz.wordpress.com/2014/05/26/only-owner-can-close-workitem-advisor/ and this shows the API to get the parent work item https://rsjazz.wordpress.com/2012/11/27/resolve-parent-if-all-children-are-resolved-participant/