This repo contains sample code for extending Visual Studio's Solution Explorer.
Here is a screenshot of a new .NET 5 Console App with this repo's code running. Each "Sample Item" has been added by this code, with random icons/overlays/state icons.
The code contains comments to help understand how to get the most out of these APIs.
When reviewing the code, it makes sense to start with SampleAttachedCollectionSourceProvider.cs.