Try to get an XML of the project.
Open in TextWrangler (cause it diplays the formatting better than other text editors).
Look for "<effect" at the top part of the XML, all are listed by name and installation path.
I exported a XML and then used you XFX Handler. Really helpful.
I wonder why FCPX doesn't prompt you when it loads a project and doesn't find a plugin. It seems like such a basic feature...
Thank you again
You may try my X-Library Check. No need for XML.
This mini-app searches a library (.fcpbundle) for all fonts and external motion templates, lists them and warns if something is missing.
Application usage: Use Menu / Button to open a Library or drag Library to the App's Icon and wait a bit. The result/report is saved as "Library Name" & "-check.text" at the Finder level of the library.