Yes, it was a huge amount of work, believe me!
I am not speaking of the code size there, but the complexity of interaction with low level COM programming and the IShellFolder interface using $IShellFolderGUID = GUID$("{000214E6-0000-0000-C000-000000000046}"), with a tool (PB6-PB7) that was not towered to low level COM programming.
Note: zBff is not freeware, but it could be used for free with either WinDev or C#.
Indeed zBff and its extension ZAP Media Browser is able to do, all what could be done with Explorer!
ZAP Media browser uses several thread to monitor disk activity and USB port detection, as well as CD/DVD insertion etc.
The problem for thinBasic, is that I didn't wrote any example showing how to use it with PB.