Adding a right-click menu item?

The architecture here is only slowly making sense to me... anyone know how you can use a plugin to add custom items to show up in the various right-click menus that are used in the manager?

Or how to modify some of the manager forms (e.g. add an extra field here and there)?

Thanks!

I hate bumping posts like this, but this seems like such a useful and critical point to tie in custom functionality... seems like there should be an event that developers should be able to tie into.

How about this:
http://rtfm.modx.com/display/revolution20/Adding+Custom+Fields+to+Manager+Forms

I can build a right-click menu for a CMP but can't think of an easy way to add to an existing menu though...

Interesting... what I was hoping for is a right-click menu item that appeared when a user wanted to add a new document of some sort. Instead of the built-in Document, WebLink, Static Resource, and Symlink, I'd like to add another item to add my own customized type of content -- the right-click menu item might read "Create Book", and when clicked, it could pre-select a template with all the custom fields for a book. It would just make for a cleaner UX.

I have searched for ways to add a CMP to the right-click menu but can't see how this can be done. Or does it get added when a CMP is created?

The Articles custom resource type adds itself to the create resource menu. Maybe you can see how it does it.