When adding a control to a form design, a very long list of control names opens a single column. This requires scrolling, takes time to locate the right control at it provides no information about controls apart from names.

I suggest this:
- Stop displaying the list of controls as a mere combobox. Either use the Toolbox window as usual in Visual Studio, or create a dialog form.
- Add the option to filter controls by name, as usual at other places. This would be a huge improvement.
- Consider grouping controls by certain common properties, such as container controls. Inspiration can be taken from the Windows Forms toolbox in Visual Studio, for example.
- Display extra details of the highlighted control. This would allow showing extra information helping with choosing the right control, both as text and images. It may say how controls are intended to be used, why one should pick "Hierarchical Grid Common" rather then "Hierarchical Grid", for example, showing a warning that a control is deprecated, maybe including the name of the containing package and so on.

Changing the visualization and implementing filtering should be relatively straightforward. Displaying extra information such as documentation would require adding such details to form controls, but it doesn't have to be done all at once. If a control doesn't provide any extra details, the dialog will simply show its name and nothing else. It won't break anything.