- Window > Show View > PDE Runtime > Plug-in Registry
- Filter to show the Plug-in(s) in question
- Right-click > Show Advanced Operations
- Choose "Diagnose"
I'm not sure since when this functionality is available (I was running 3.4RC2), but a big THANKS goes to the PDE team for this (and I assume that Chris Recoskie will be especially happy about this).