usage view follow documentation view cursor

[keith]

The new feature you added to have the cross reference view follow the ladder cursor is cool.
Beets AB's style of clutering up the ladder view with the cross reference information.

What about a way to make the cross reference/usage view follow the documentation view ?

In particular, it would be nice to have a way to know that an undocumented resource is not
being used.  It is also usefull to know if a used resource is documented.

This is perhaps more useful in the usage view rather than in the cross reference view.