A new Haptic Touch feature can be used to expand notifications on the iPhone XR if it's running iOS 12.1.1 or iOS 12.1.2.
The feature is similar to 3D Touch, a feature found on older iPhone models where a long press brings up new controls. The iPhone XR doesn't have 3D Touch so this is the next best thing.
Unfortunately, Haptic Touch only works in a few places at the moment though Apple plans to expand it across iOS down the line.
Haptic Touch is limited to newer iPhone models and won't come with older phones that lack Apple's 3D Touch functionality.
If you skipped iOS 12.1.1, download iOS 12.1.2 for access to this feature.