Apple has released firmware version 2.2.2 for the Pro Display XDR. According to Apple’s release notes, it:
Adds support for customized Pro Display XDR reference modes that you can tailor to specific workflow needs by setting color gamut, white point, luminance, and transfer function options.
Offers Minor stability improvements.
The firmware update requires macOS 10.15.4.
When a firmware update is available for your Pro Display XDR, you might be prompted to restart to apply the update. Otherwise, the update is applied the next time you disconnect and reconnect your display from power or your Mac.