I found this under Capabilities in the App ID configuration. The help text says it can be used on both iOS and macOS. What is it good for? How can I take advantage of it?

I am trying to get the File Provider extension to work on macOS 10.15 Beta 7 (19A546d) with Xcode 11 Beta (11M392r) so far did not manage to get it to launch with a sample project. The documentation is very lacking and there must be something I missed.I have a Mac app that does the following on launch:let domain = NSFileProviderDomain(identifier: NSFileProviderDomainIdentifier(rawValue: "com.app.testfileprovider"), displayName: "TestFileProvider", pathRelativeToDocumentStorage: "") NSFileProviderManager.add(domain) { error in if let error = error { NSLog("Could not add file provider for domain: \(error)") return } guard let newManager = NSFileProviderManager(for: domain) else { NSLog("Could not create file provider manager.") return } self.manager = newManager NSLog("File provider URL: \(newManager.documentStorageURL.path)") }I sometimes get this error, not sure why:Could not add file provider for domain: Error Domain=NSFileProviderInternalErrorDomain Code=3 "The value “com.myappbundleid” is not valid for the parameter “callerBundleID”." UserInfo={NSLocalizedDescription=The value “com.myappbundleid” is not valid for the parameter “callerBundleID”.}The error may be resolved by a "killall Finder" command in Terminal, then it runs successfully, and outputs:File provider URL: /Users/[username]/Library/Group Containers/group.com.myappgroup/File Provider StorageIn Finder the “File Provider Storage” folder appears with a cloud badge, which seems to be OK. I guess.I have my File provider extension class, which is basically the generated code when I added the File provider extension to my Mac app in Xcode:class FileProviderExtension: NSFileProviderExtension { var fileManager = FileManager() override init() { NSLog("File provider initialized") super.init() } ...Here the “File provider initialized” message is never logged and the extension is never initialized. I cannot get it to launch at all.In the Console.app this is the only relevant message I could find:default 09:14:35.447849+0200 *** com.apple.launchservices - 45683955: Checking whether application is managed at file:///Users/laszlo.agardi/Library/Developer/Xcode/DerivedData/FileProviderMacTest-eebpahoydvfxovantvhkplhgrcty/Build/Products/Debug/FileProviderMacTest.app/Contents/PlugIns/FileProviderExt.appex//com.myapp.fptest.FileProviderExtWhat I did so far:the app and extension are sandboxed, it is set in the entitlements filesthe app and extension share the same app group, also set in entitlementsTried to launch the extension: Run the file provider from Xcode, Xcode was waiting for the extension to launchI opened the File Provider Storage folder in Finder, it has the cloud badge. But no file action inside or just browsing launches the File provider extensionWhat am I missing? How do I get the File Provider extension to launch on macOS Catalina?