-Hi, my name is Claudeir, I'm happy to help you!
This function is not possible because when opening an MP4 file, the system identifies that you just want to watch and not edit, if you want to edit, for a faster way, fix the Windows 10 Video Editor in your taskbar or in the Start Menu, you will have to open the Video Editor app and then Start the editing project through the app.
But I found your question interesting, if you have any ideas to pass on to the developers, feel free, using the shortcut Windows+F, you can send your comment.
-Feel free to leave your opinion, marking as answered if the answer helped, or leaving more details so that we can continue the service, this is very important to us.
Graciously,
Claudeir