在Panel上使用C＃WinForms Designer而不是Form Again？

I have the same question, but the answer to use a UserControl will not do. I also need to create a control container that I can add other controls to at design time so I can add it to yet another container (Splitter Panel) which is not avaialable to me at design time (plugin architecture). When I make a User Control, it is missing the design time support and all I get are icons when I drop controls onto this surface.I have the same question, but the answer to use