Please investigate how the "activeRowActionOpenCard" button was added into the "SupplyPaymentDetailV2" module. Please feel free to create your own container and apply your CSS in order to create the left button. The handler for the buttons is in the "onActiveRowAction" method in the "ConfigurationGridUtilities" module. Please put a breakpoint and click on the button on a record in the "Installment plan" detail on the "Order" page. You'll see how to handle the click. Please note that you can override the "onActiveRowAction" method on the detail schema.
Please read bpm'online development guide for more information.