Since the v1.10 of Storyboards, there is a new option for each layer that controls its focus.
By default, all layers are in focus. To set a layer out of focus:

1- Select that layer (tap the Layers button and tap the layer that you want to select).

2- Tap the arrow button to the right of the drawing title and tap Layer: Edit properties. Then select the level of focus you want for the layer.

3- When you save the properties, nothing happens. It’s when you switch to another layer that the layer is rendered with the out of focus option.