A simple question - Can I copy/update/change Sonars Default Effects list?

You already know about custom plug-in layouts so I assume you are asking about the "Default All Plug-ins" layout. This layout is created on the fly and does not exists as a layout file.

scook
You already know about custom plug-in layouts so I assume you are asking about the "Default All Plug-ins" layout. This layout is created on the fly and does not exists as a layout file.

Yes exactly.  the "Default All Plug-ins"  is missing plugins.    Imagine that.
 
I would have liked to be able to edit it.

It seems unusual that the layout would be missing plug-ins. The layout is built from the VST inventory in the registry, registered directX plugins and the FX chain folder. If you feel it is actually missing plug-ins which are not in the exclude list and did get scanned or registered correctly, it would be a bug which needs to be reported.

I guess you have run a VST reset http://www.cakewalk.com/S...ommended-for-Upgraders