Currently it looks like the DecorationProvider api, only applies to the explorer file tree. Can this be expanded to apply to custom view trees as well?

Maybe expand to include an optional viewId

registerDecorationProvider(provider: DecorationProvider, viewId?: string): Disposable

The DecorationProvider.provideDecoration will also need to be updated to support TreeItem (or the item element itself?)

provideDecoration(uriOrTreeItem: Uri | TreeItem, token: CancellationToken): ProviderResult<DecorationData>;

Also while its probably not ideal, I did wonder if setting a resourceUri on a TreeItem would trigger the decoration, but it doesn't either.

/cc @sandy081