How to Enable confirmation pop-up while Reject the task in worflow?

Article - "How to display a confirmation popup at the end of a customized wizard rather than an Inline Message in Windchill": https://www.ptc.com/en/support/article/CS151142 

Hi @vshanmugam 

You can use the Article CS44140 to add an alert for the complete task button.

Instead of alert I recommend to use a confirm("Do you want to continue ?"); 

next you can use also js functions to get the page information what has been selected so you can put a condition if the confirm message should be shown or not.

here is an example how to use the confirm function How to use JavaScript to show a confirm message.

PetrH