Is Shipping Rates Calculator+ compatible with pop-up carts?
On some themes, Shipping Rates Calculator+ will display the shipping widget on pop-up carts, although it depends heavily on the theme layout.
Most complex themes or customized pop-up carts could not be supported right out of the box.
The app is regularly updated to add new features and adapt its code to the latest changes on Shopify, so we could add support for more pop-up carts as new themes are published on the theme marketplace.
However, please also note that Shipping Rates Calculator+ has a setting called Drawer and pop-up carts support that will allow you to disable the widget on other pages different from the cart page. By enabling/disabling this option, you can avoid possible issues with unsupported pop-up carts.
You can find it in the Advanced preferences section of the preferences page: