The filter Library is just ONLY ONE, this is shared between the standalone and the plugin
8bf file which contains the Filter Forge plugin and then copy it to the plugins folder of Photoshop, so then is possible that Photoshop can see Filter Forge. You can´t scan for the search of plugins, BUT there is a possible workaround that could work. If you have installed Photoshop AFTER installing Filter Forge, Photoshop will NOT have the filter forge plugin becuase it is installed when you make the Filter Forge installation.