How can you select all objects on a sub-layer and change their opacity?

To select all objects on a sub-layer and change their opacity, holding down the shift key while clicking on the layer is an effective method. This action typically allows you to select multiple objects and is a common technique in many design and graphics software, including Adobe Illustrator. This method is particularly useful because it lets you quickly select everything contained within the targeted layer or sub-layer without needing to navigate through additional menus or double-clicking on layers.

This technique can streamline your workflow, especially when working with complex designs that contain numerous elements on various sub-layers. After selecting the objects, you can easily access the opacity settings through the Transparency panel to make adjustments as necessary.

Other methods may involve additional steps or do not allow the same level of direct control and efficiency when selecting multiple items within a sub-layer.