Welcome @Strash! Some thoughts I have on your mockup:
For a large project you will likely have both a long list of Assets and probably also complex scenes which will result in a long Outline. Wouldn’t it be harder to get a good overview if the Assets and Outline is in the same panel?
Another thought. When you select something in the Outline (or in the scene) the properties for that component or node is shown in the Properties panel. This makes me think that there’s a closer connection between Outline and Properties than between Assets and Outline, and to me it makes more sense to have Outline+Properties together like they are today.
One improvement I can think of is to hide/minimize the Properties panel when nothing is selected. This would give me more space for the Outline.