On Wed, 18 Aug 2021, at 5:34 PM, Graham Brown wrote:
What am I missing?
You're not missing anything. Visual inheritance in the Windows Forms designer does not work like VFP, Delphi or whatever. It didn't in 2002, and on inspection still doesn't now.
This is how you do it with a UserControl.
https://docs.microsoft.com/en-us/dotnet/desktop/winforms/controls/creating-a...