Sorry, I do have some answer, but it is not going to be very good. Hope, it may help.
I know two approaches.
One of them is using
CommonDialog.HookProc
method.
I never used it, but saw some relevant works on CodeProject.
This is one:
Extending the save file dialog class in .NET[
^].
(Do you need System.Windows.Forms? WPF is another story...)
Sorry, this is about safe file dialog, not folder dialog, but perhaps you will be able to catch the idea. Also, you might search and dig out some more similar solutions to find something closer using the same idea.
Another approach is... making all the functionality from scratch. You know... not so easy... can be out of style...
Unfortunately, it does not look that painless way exists.
Any other idea, anyone? Would be highly valuable.