What is the keyboard shortcut to start a screen recording (not open it)?

Mac keyboard shortcuts - Apple Support

//support.apple.com/en-us/HT201236

Most of those should be first across timeline.

[Since I've no use of recording, be my guest!]

A button appears in QuickTime to start recording.

Use QuickTime Player(?)

1. Open QuickTime Player from your Applications folder, then choose
2. File > New Screen Recording from the menu bar. You will then see either the onscreen controls described above or the Screen Recording window described below. 
3. Before starting your recording, you can click the arrow next to the Record button to change the recording settings:
4. 
   

• 
• To record your voice or other audio with the screen recording, choose a microphone.
• To monitor that audio during recording, adjust the volume slider.
• If you get audio feedback, lower the volume or use headphones with a microphone.
• To show a black circle around your pointer when you click, choose Show Mouse Clicks in Recording.

To start recording, click the Record button  and then take one of these actions:

• • Click anywhere on the screen to begin recording the entire screen.
  • Or drag to select an area to record, then click Start Recording within that area.

1. To stop recording, click the Stop button  in the menu bar, or press Command-Control-Esc (Escape).
2. After you stop recording, QuickTime Player automatically opens the recording. You can now play, edit, or share the recording.

How to record the screen on your Mac - Apple Support

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