The z-coordinate at which to place this button relative to its parent when the button is enabled and has a pointer hovering over it.
This controls the size of the shadow below the floating action button.
Defaults to 8, the appropriate elevation for floating action buttons while they have a pointer hovering over them. The value is always non-negative.
- elevation, the default elevation.
- highlightElevation, the elevation when the button is pressed.
- disabledElevation, the elevation when the button is disabled.
final double? hoverElevation;