Here is some part of my webinar on GH Custom Control library . You can find out how to :

• Create and add a control to Grasshopper component
• How to stop a control from updating solution 
• How to group controls.
• How to layout controls. (stack panel)
• How to listen to control events. 
• How to build your own Custom control.

Please excuse me for the background noise , all of a sudden a construction site just began next door!