[racket] Pretty-printing properties in syntax browser

I’m putting large s-expressions as properties on syntax objects.  When I display them in the right pane of the syntax browser, they go way off the side of the pane.  I’d like to be able to pretty-print the values of properties.

I can’t figure out how to insert pretty-print into the property display routine.  Any ideas?

[I accidentally sent this to dev rather than users.  Sorry to those who get it twice. — Byron]