When you want to find a part in your model tree to change some constraints, you can do it in a few ways. If you know the parts' names, you can simply search for them using the search function. When you know which part it is in your assembly, you simply click it, and the selected part lights up in your model tree.
But when everything is sorted into folders, and you don't know the name of the part you're looking for, but you know its location on the screen, then it's hard to find your model tree. You can try to figure out the name or search through all your folders. Both of these are tedious exercises, and it can be so much easier. Make that folder, which contains the part you're looking for, light up when you select it on your screen. In that case, it is immediately clear which folder the part is in. If the folder is in a parent folder, let the parent folder light up too.
