If your Huawei device is on standby, you can take a picture or open up the camera app by pressing the volume down  button twice. This works only if Ultra snapshot is activated.

Android 10 | EMUI 10.0
Step 1:  Open  Camera
Step 2:  Open the  settings
Step 3:  Tap on  Ultra snapshot
Step 4:  Choose  Take a snapshot ,  Open camera , or  Off
  1. Open Camera
  2. Open the settings
  3. Tap on Ultra snapshot
  4. Choose Take a snapshot, Open camera, or Off

Huawei Instructions