And if you haven't done it already, you'll probably want to create a new command in the CUI that runs the EDITLABELTEXT command, then add that command as a double-click action to various C3D elements, as shown in the attached image.
This will let you double-click on C3D labels to edit the text, which is not default behavior for some inexplicable reason.
(Note that if you aren't sure what name to use as "Object Name" for various labels, pick one in the drawing and run the LIST command on it.)