Hi Kevin,
It depends which type of extension you are referring to. JavaScript extensions can have their scope changed to preloader, but most other extensions can only be used in All Tags scope, or scoped to individual tags. As far as JS extensions go, preloader extensions are run in global (window-level) scope, so you need to make sure that you code accordingly, and that you are not using any references to the "b" object (it doesn't exist at this point).
Perhaps you can share more details about what you're trying to achieve so we can guide you towards the best solution?
Thanks,
Craig.
Check out our new Swift integration library for iOS, macOS, tvOS and watchOS: https://github.com/Tealium/tealium-swift with updated
documentation https://community.tealiumiq.com/t5/Swift/tkb-p/swift.