@KavinrajT-150407  you would need to run an activity to on click on this button to create a payment child case to this parent case and the payment screen should be routed to this same user. You can use pxAddChildWork activity. 

You can also change the submit button name to make payment and on clicking that button flow will be advanced and you can use create case smart shape. 

Hi @KavinrajT-150407: Can you please check the implementation of Case wide supporting process. You can create a simple flow with a create case (as child case) automation in it. Once the flow is available you can use "pega.ui.HarnessActions.addFlowFromActionsMenu" script to invoke the flow to create case.

Refer "WorkActionsAddWork" navigation rule. (Referred from Actions menu in case)

Also please check if changing the button name in the flow action and proceeding the case flow to create child case helps.

Thanks.