Single sprite, single behaviour widget (all the components - the drag handles, text input, scratch board - are handled with imaging lingo and internal callbacks). Have a play with the Director 8.5 source (ZIP archive).
Incidently, creating complex widgets that can be encapsulated into a single sprite with a single interface would be much easier if Macromedia improved Director's handling of LDMs (Linked-director-movies). Think movie-clips in Director.
As with all the source code provided, there are no warranties express or implied. Use at your own risk.