Toggle Metal API Validation via your Xcode Scheme:
Scheme > Edit Scheme… > Run > Diagnostics > Metal API Validation.
It’s a checkbox, so the possible options are Enabled or Disabled.
Disabling sets the key enableGPUValidationMode = 1 in your .xcscheme file.
After disabling, Xcode no longer logs the “Metal API Validation Enabled” log message.
Note: In Xcode 11 and below, the option appears in the “Options” tab of the Scheme Editor (instead of the “Diagnostics” tab).