In an effort to add more projectM visualizations to VLC (besides the included one), I downloaded projectM from Steam and specified its presets folder as the value for "projectM preset path" in VLC's preferences (Tools > Preferences > Show settings: All > Audio > Visualizations > projectM > projectM preset path: C:\Program Files (x86)\Steam\steamapps\common\projectM\presets). Then I played an audio file and started up the projectM visualizer, but only got the same built-in visualization!
This led me to believe that VLC does not use recursion (i.e. search in subdirectories) when looking for projectM presets in the specified path. So, I figured I'd try to copy all the files from all the directories and just store them into one large directory. However, when I looked at the property sheet for the source directory, it showed me a total of a whopping 9,791 FILES in 193 subdirectories! I figure it is not humanly possible to COPY almost TEN THOUSAND FILES from almost TWO HUNDRED FOLDERS and expect to throw them all into just ONE LARGE DIRECTORY!
So, instead, I hope that this little oversight can be resolved soon.