I want to know how to save animate videos in mp4 format.

The way I do it is this.

1: Turn off Advanced Layers to improve general performance.

2: Publish as an SWF file.

3: Use Swivel to convert to MP4. https://www.newgrounds.com/wiki/creator-resources/flash-resources/swivel

Building on the third step, Swivel is what many animators including myself use to convert our Animate videos to MP4. It will render out your animation frame by frame while maintaing full quality. There is a tutorial by Alan Becker on YouTube on how to use it.

I'm currently developing a process for converting a series on animated lessons I've composed into MP4/HTML/CSS/JS files.  I tried using the Export Video/Media function of Adobe Animate, but I encountered numerous problems, including poor resolution, loss of ActionScript, and only exporting the first sceen.  If anyone has advice for avoiding these problems I would very much like to see it.  Instead, I've had much more luck using a Windows utility called GameBar to capture the video as an MP4.  To activate it just click the windows and the g keys simultaneously.  You lose your ActionScript, which is why I'm learing HTML/CSS/JS to restore user control, but the fidelity is very good.  You will also need a video editor to crop and trim the excess.  I use a program called VideoPad ShotCut.  Adobe Premier Pro is another, more robust product.