I’m not sure if this has anything to do with Mac or Windows, but I believe there are two ways to create a “complete” file for the DefaultLibraryAdditions folder discussed earlier in the thread: either export a library from Dorico Library Manager and pair it down to the 3 components or take an existing single instrument file and add components to that instead.
However, there is an important caveat: when exporting a library using Library Manager, the resulting xml (a .doricolib is a renamed xml file) would contain this node name:
Making instrument edits and additions in a file with this node name and then placing this file into DefaultLibraryAdditions will not work - Dorico will throw a warning and exit.
In order for everything to work properly, the “kScoreLibrary” node should become the topmost node, like this:
This library made by @benwiggy worked perfectly for me - I simply deleted all the sub-nodes in the tree to only retain instruments, instrument names and instrument families.