Can PGenerator on rpi4 (which I have) send the same patches simultaneously on both HDMI outputs?

I want to try perceptual color matching on an OLED display (with a LCD display as "master"). How do I put up an identical patch on both displays? If PGenerator can handle this then it is solved. But I need to purchase an (extra) micr HDIMI adapter to try, so I ask here first. If this is not possible, is there another easy way to put up those two identical patches?

Use an HDMI splitter.

The HDMI-A1 is the correct port to use, not the other.

Do remember that splitters will normally use the EDID of the least-capable screen to limit the signal for both displays in order to keep from sending that screen a signal it cannot handle. So if one is 1080p SDR and the other is 4K HDR, only 1080p SDR can be sent to both.