The partial shading follows the same "mechanics" as attributes if you are familiar with those...
If you set the partial shading setting in the leaf part, it will be partially shaded in any assembly above , including the drawing.
If you set it on "a component" it will only be partially shaded in this assembly, and since a drawing is an assembly in technical aspects, you need to assign the setting in this assembly ( =The drawing) if you haven't done so in the leaf part. - Clear ?
The setting is "instance specific" which means that if you have 4 identical components ( same leaf part,4 instances) you can assign the PS on "any" of the 4.
In the leaf part, select the body ( or the relevant faces) and Edit- Object display - Partially shaded= on
In the assembly select the component ( or the relevant faces of the component) -"-
Note that if a leaf part is toggled "partially shaded", you can in any assembly toggle off the PS in this specific assembly, the PS will "re-appear" in the next level.
regards,
Tomas