Another way to do it is click Flight Plan then Add Waypoint and type in the intersection name. It will be added to the end of your flight plan. You can then move it up the flight plan as necessary. I'm not saying your idea is not a good idea, but this works for now and is easy to do.
You can also click Opt next to your previous waypoint in the flight plan then click Insert Waypoint After.
Or, you can simply drag your course line to the waypoint and enter it that way, but you would obviously need to find it first.
By the way, these methods work with the fixes on the overlaid approach plate also.