+1 and bump 
not sure if this has been implemented but it does not seem so. In the process of setting up the Obj-c workaround above but would love some juce 6 to the rescue …
EDIT: another possible user preset road ahead would be for juce to support the ‘shared user presets’ feature
https://developer.apple.com/documentation/audiotoolbox/incorporating_audio_effects_and_instruments
Don’t know how painful that would be, but maybe it’s a more “official” way than working around with file paths and security groups