Hello,
Our developers checked the code of your plugin and found that it plugin has condition for option to show/not show quantity -> https://prnt.sc/qfJB5eOGo9CY That means after you make this select to yes value -> https://prnt.sc/gN2FDhw4oUAQ and save components you will have quantity on each product in both cases (Single Product builder or without) -> https://prnt.sc/HcFCUpgIc8II The code you had before makes no sense because it plugin there are no conditions for such filters.
Regards