Requirement : An agent is getting the work item , but he/she is not approving / rejecting the same, in this case system is keep on sending the reminder mail in every 12 hours until he / she act on the workitem. Once the workitem is approved / rejected  then only the control pass to the next step. Please find the template below followed by the step description

Before the release step , I added a fork having two parallel branch with one necessary branch. In one of the branch I put the release step and rest of the operation and in another branch created an infinite loop step within this loop created a dummy method and two mail step ( one to SAP inbox and the second one to External mail ). In dummy method , I selected the Requested Start tab and put the work item creation and time after 12 hrs. ( please see the below screen shot ).

So whenever the Agent approve / reject the work item the fork will end OR every 12 hours the mail is keep on sending mail to the agent ( to sap inbox as well as external mail ) as a reminder until he approved/rejected the work item