I want to be able to highlight some objects red, or put an icon next to them in the project pane. Is there some UnityEditor function that will let me do this?
I don’t have the answer right there, but I know you can look at the code in the serializer tool here : http://whydoidoit.com/unityserializer/getting-started-guide/
(Great tool btw) and he is using some icones to display next to the files. I don’t think this is in the project view, but instead used in the hierarchy panel.
Maybe it’s a good start for you.