Sorry for the long delay, updates to Unity and the SteamVR plugin broke my existing build, and I only recently found a way to get things working again. Once I did, I was able to complete several things I had in progress, and add many new things as well. So, on to the patch notes:
* Added a file navigation system above the active directory bar, letting the user open folders in a directory or navigate to root folders. The contents can be loaded using the Open button at the top.
* The file navigation window has a scroll bar for when there are too many folders to show at once.
* Added buttons for navigating up one directory, or returning to the previous open directory.
* Added a Favorites panel to the right, where the current directory can be saved for easy access later. Favorites entries can also be removed.
* Added Index controller support. The Index controls can be seen by looking in back, pointing at the corresponding button, and pulling the trigger.
* Fixed issue loading files and folders with certain problem characters.
* Updated UI elements with higher-detail graphics.
* Highlighting folders and files with long names will show the complete name.
* Added tooltips to several buttons.
If anyone's still following this, I hope you find the update useful. In case Steam doesn't automatically update the application, uninstalling and reinstalling it worked for me.