The Windows Forms out-of-process designer is currently available as a preview Visual Studio feature in Visual Studio 2019 or later. It can be enabled in Tools -> Options -> Environment -> Preview Features dialog by checking the Use the preview Windows Forms out-of-process designer for .NET apps checkbox. Releases of .NET Windows Forms Designer are tied to Visual Studio Preview releases, so update to the latest Visual Studio Preview version to get the newest designer features.
❗ The latest designer feature shipped in Visual Studio 2022 v17.5 Preview 3 is Modernization of code-behind generation.
For the latest news on the designer please refer to the series of blogs:
- Custom Controls for WinForms' Out-Of-Process Designer
- Visual Basic WinForms Apps in .NET 5 and Visual Studio 16.8
- Databinding with the OOP Windows Forms Designer
- State of the Windows Forms Designer for .NET Applications as of 01/13/2022
For more information about creating custom control libraries, including sample code and templates refer to the WinForms Designer Extensibility Repo. Details about how to use the WinForms Designer Extensibility SDK and structure a control library nuget package can be found there as well. Download the Extensibility SDK from NuGet.