Please add a feature where I can right click on an mp4 within a powerpoint and have the option to save as mp4

Once you have opened that PowerPoint presentation in Keynote (v14.1), click on the .mp4 movie to select it and then click the Movie tab in the Format panel. Directly beneath File Info, you will see a small generic icon and the Keynote name of that .mp4. Click once on that image icon and in one continuous motion, drag and drop to the Desktop. That is how you get images and movies out of Keynote.

Although the .mp4 movie retains its original filename in PowerPoint, when you open the PowerPoint in Keynote, the original movie filename is lost and the first movie assumes the name of media1.mp4 in Keynote.

Check the file type - Keynote can save a presentation as either a 'single file' or 'package'. My technique only works for Package types (which I *think* is the default), but importing may change that.

Do you want to export just the .mp4 as a file on its own?

Or are you trying to export the presentation as an .mp4 showing the video running within the presentation?

If the former, you can extract the .mp4 (or any media) via the Finder.

Find your .key file, Ctrl-Click it and select 'View Package Contents'. This will open a window showing the contents of the .key file, including a Data directory. In this directory are the raw images, movies, audio files, etc. that are used in the presentation. You can just copy the file out of there to any other location on your desktop. Maybe not as streamlined as saving it from inside Keynote itself, but not overly complex.

FWIW, the Export -> Movie option is designed to save a movie version of your presentation playback, not to export individual pieces of media, which is why it doesn't work as you expect here.

Nice. I admit I'd never even noticed that.