What is the best way to navigate MP4 call recording without having to see a notification every time you start and end one?

It's part of compliance as well. It has to be notified to the participants that the call is recorded especially when they are in GDPR zones. Please check with Cisco WebEx team directly if this can be turned off exclusively for you (customized).

If you're referring to the Recorder banner/pop-up that appears along the bottom of the meeting window when you start recording, I would say no. I would think that would be a system programming issue that needs to be directed to Webex Support. I've wondered myself why it doesn't disappear after you start recording, especially since there is a recording notification in the upper right corner of the meeting window. That being said, you may can avoid the banner altogether by enabling Automatic Recording under Site Configuration but there are other considerations that have to be made when working with that option.

I don't know that it can be turned off. My understanding is that it is like the beep at the beginning of a recorded call. The purpose is to notify everyone that the call is being recorded. You may want to contact Cisco support to see if they know of a way to turn it off.