Sandboxing: How to use URL Bookmarks for Mac as well as iOS?

So I’m working on a sandboxed Mac AUv3 plugin. It’s a sample player plugin that requires a bunch of audio files to be stored in directory structure which the app has access to. When the plugin first runs, I ask the user to specify where they would like to store their sample library, and this gets me access to that directory regardless of where it is in the file system. The problem is that the next time I run the app, I no longer have access to these files.

According to the Apple engineers I spoke to at this year’s (virtual) WWDC , I need to store the “bookmark” for the files and use that instead.

How do I do this within Juce? All of the bookmark functionality in URL seems to be #ifdef JUCE_IOS. Is there something I’m missing?