Hello, Juergen,
Thank you for contacting us and for using XStore.
1/ Navigate to XStore Builder and select the Checkout page. Here is a screenshot for your reference: https://prnt.sc/NoS-O8_UHX2y. You will need to replace the default shortcode with the Checkout page element. Subsequently, choose the desired position for the Coupon. You can see an example here: https://prnt.sc/bHpTM7uKl5BW.
2/ We regret to inform you that the option you are inquiring about is not available by default.
Kind Regards,
8theme team