I would like to see the ability to use the same surface treatment / finish / color etc for multiple parts. Unless I'm missing something, you seem to have to "paint" every unique part separately and if you miss one, you have to remember what color / finish it should have. If you could copy the finish properties from one part to another, this would ensure the correct match.
Shift left click to copy, shift right click to paste and link, or shift ctrl right click to paste only. Or you take the material you assigned for the first part from the in project material library, and drag it onto the other parts. These will then also be linked.
You can also select multiple parts in the scene tree, and drag a material from either library onto the selection set. This will pain them all the same material and link them.
You can always unlink using right click > unlink material.
Hope this helps.
Thomas
You can also make up a 'custom' material and save it to the material libraries.
Also, if you often render similar assemblies you can apply materials/maps to the parts initially and save that setup (named parts and associated materials) as a 'materials template' - it can be a great time saver ;)