Need control authoring articles for new WinForms Core designer

You have very good set of topics on what control author should do to show third-party controls at design-time, work with different design-time features, show toolbox icon etc.. But is all about old .Net framework controls: https://docs.microsoft.com/en-us/dotnet/framework/winforms/controls/developing-windows-forms-controls-at-design-time

For .Net Core 3 and .Net 5 you changed design-time model. We already see that some part of it working in VS 2019 preview. It would be nice to start updating documentation as well. What should we do to support new designer? How to pack design-time assemblies? How to implement designer actions or custom designers? Etc..

It would be great if you can start at least with few very basic topics and evolve them later