Back and forward buttons for the Unity project browser
Only works in Two Column Layout (not the skinny layout).
Tested in Unity 2018.2.14 with .NET 4.x scripting runtime. Previous/future versions may or may not work depending on how much Unity changes their code.
Download the two cs files and put them in an Editor folder.
Example: in "Assets/GreatFolderName/AnotherFolder/Editor/"