Creating a fallback option for a Playback Template

I want to have BBCSO instruments assigned to all the staves in a score that correspond to BBCSO instruments whilst assigning Noteperformer to be the fallback option VST playing all sounds not in BBCSO library (e.g Piano). I have in my Play/Playback folder An option ‘BBCSO + Noteperformer’ that only loads BBCSO sounds It does not load the piano into Noteperformer
I remeber reading something about a default playback template being assignable but I cannot remember how to implement. I would appreciate some help with this If anyone knows how to do this I would appreciate their input.

John Barron explains it in the Discover Dorico session about playback templates.

Here’s the 3.5 documentation for the Edit Playback Templates dialog, in case that’s also helpful.