Is there any way to change where an exit goes? You can create an exit, but there is no "destroy exit", or "change exit". And I can't even quite figure out how how to make exit invisible.

If you want to change where an exit goes, you could just use something like this

exit_name.to = room_or_object

The 'to' attribute says where the exit goes, so when you change that, you change where the exit goes.
As for making an exit invisible, you can use the 'Make exit invisible' script (in the Objects section of the menu)... Just remember that you have to give the exit a name first to be able to change its visibility.

Thank you. That is what I was missing, the fact that you can give an exit a name. That makes it very easy.

To actually destroy an exit, use:

destroy (exit.name)