How do I manually associate an iOS app counterpart to my macOS app to deduplicate Notifications from iPhone?

Howdy,

I'm trying to figure out how to replicate the following behavior for our app:

The system is able to ascertain that the Mac equivalent of some iOS app is installed locally, and it prevents notifications from being mirrored. However, I am unable to determine how this association is inferred. When I check our iOS app under this prefpane, the switch remains enabled and toggleable—we'd like to act like Slack here.

My initial assumption is that an app group containing both the Mac and iOS apps can be used to create the association; however, I would like to confirm that this is indeed the case before doing so. I'm not terribly confident about this.

Details:

• The bundle identifiers of both apps do not match. This also applies to Slack; its iOS app is com.tinyspeck.chatlyio while its Mac app is com.tinyspeck.slackmacgap.
  • In our case, the iOS app's identifier is like com.company.app while the Mac app's identifier is com.company.app.desktop.
• Both apps are signed with certificates that have matching team identifiers. The com.apple.developer.team-identifier entitlement is present on the Mac app.
• The Mac app shares a keychain access group with the iOS app.
• The Mac app is not sandboxed.
• The Mac app is an Electron app.
• The Mac app does not use APNs. It sends notifications "locally".
• I currently only have the iOS app installed on my iPhone via TestFlight, if that matters.
• Notification mirroring does work, but we'd like to forcibly disable this by associating the apps together.
• To my knowledge, the iOS app makes use of both a UNNotificationServiceExtension and a UNNotificationContentExtension.
• The iOS app currently doesn't have an assigned category (at least in Xcode). The Mac app is currently miscategorized as a developer tool (LSApplicationCategoryType = "public.app-category.developer-tools";), but that should be fixed.

(Redacted) bundle information for the Mac app:

• CFBundleDisplayName = App;
• CFBundleExecutable = "App Desktop";
• CFBundleName = App;

Note that our CFBundleExecutable differs from the bundle's display name/name because we're currently migrating our users to a new version of the app that they'd likely want to live alongside the new one. The filename of the bundle itself is, similarly, App Desktop.app.

For the iOS app, to my knowledge, the CFBundleName and CFBundleDisplayName are App.