I finally found some time to keep working on this.

I reworked the patch with the useful suggestion from Basil.  I think I
addressed all the points raised, and that the patch looks much better
now.  I went with `describe-widget' for the name of the command, but
have no preference over the name, so if someone suggests something
better, I'm OK with it.

If the approach of putting the variable in a preloaded library, like
Lars suggested, is better, feel free to either adapt the code
or tell me and I'll do it.

WDYT?

Best regards,
Mauro