OD+ Discovery by Accident
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WinCustomize Forums
It may be that there was documentation stating this, but you know the little problem where in the Choose Image dialog lumps every image together even if you have it all arranged nicely in separate folders within the Images folder? If you move your image folders up one level to the ObjectDock folder the Choose Image dialog sees it as a separate folder making searching for images much easier.
Good to know you've found it though!