Is there a way to make the text that you can add in the video editor apear to look 3D? I want to add 3D knock out text on top an existing video. Or is it possible to create the 3D text in the 3D viewport and somehow place it on the video in the Video editor?
Sure, create your 3D text, enable the film Transparent option in the Render panel:
It will give you a transparent background when you'll render:
If you plan to animate the 3D text, export it as a series of PNG (RGBA) pictures in order to keep the transparency:
Then in the Video Sequencer, press ShiftA to add the text, whether it is animated or not. Then put the strip it will create over the video strip: