MiniUtils is a collection of 3 Unity Editor extensions. All source code is provided.
Prefab Viewer allows deep inspection of any prefab without having to move it into the scene.
History Navigator tracks the currently selected item in the Unity Editor. Alt+Left Arrow and Alt+Right Arrow to navigate the history.
History Navigator also allows marking Unity objects such as GameObjects or Materials as "Favorites" which can be quickly accessed from the History and Favorites window.
Physics Collision Layers provides an alternate way to modify physics layer collisions. Rather than the Unity Matrix view showing all layers at once, Physics Layers Manager focuses on just one layer at a time.