This commit makes some assumptions:
- `AppSettings` is an `ObservableObject` that uses `@AppStorage` where possible, which sets default values.
- Each change to an property triggers an `objectWillChange.send()` call.
- `IconSize` is not used. Instead, it defaults to 40.0 with minimums and maximums of 20.0 and 60.0, controlled via Timeline settings.
Stuart Breckenridge