title: Does VS 2019 Designer have trouble with TabPage, UserControl, and TreeView?
body: <p>I'm encountering three issues with Visual Studio 2019 (16.6.3) Designer for .NET Core 3.1. Are these Designer problems or set-up errors on my part?</p>
  <ol>
  <li><code>TabPage</code> - Controls I drop on a <code>TabPage</code> can't be selected or modified in the Designer. I can select them in the Properties panel and change things, but no mouse action in the <code>TabPage</code> works. (Exception: If a <code>Panel</code> is the only control on the <code>TabPage</code>, I can select it in Properties and then use the mouse to drag it out of the <code>TabPage</code>.)</li>
  <li><code>UserControl</code> - Designer won't even let me begin to create a user control. When I choose Add --&gt; User Control in the project, I get nothing.</li>
  <li><code>TreeView</code> - I can put several root <code>TreeNodes</code> in the Designer and they work fine. If I add a child <code>TreeNode</code> to a root node, that root node vanishes (even from designer.cs file) when the project builds. (I have only tried this with checkboxes on the nodes, though I doubt that makes a difference.)</li>
  </ol>
  <p>This is my first venture into a .NET Core app. Am I missing something?</p>