The modals used for saving/creating views in IndexFilters is still using polaris which also means the overlay/backdrop is contained with the app iframe. There is no way to override this too as the onCreateNewView opens the modal.
Considering the Polaris Modal is now deprecated, and I assume would be a fail if trying to go for BFS, this needs updating asap.
It either needs to use the app bridge modal, or at least let us control the entire action and remove opening the polaris modal.
EDIT: It’s also not possible to handle the loading state of the button which is not great UI, we need more control of this. Changing the modal title aswell ideally. This will all be possible if we can just attach an app bridge modal ourselves and IndexFilters stops opening the polaris modal automatically.