Raspberry Pi 4 dual monitor, AP only use the second

[Knaldgas]

RPi4 with dual touch screens, Knobster, Linux and Air Player 4.1.5 (2 x 1920x1080, OpenGL ES 3.1 and Mesa 20.3.5)
Windows 11 with X-Plane 11 and Air Manager 4.1.6

RPi4 has Display 1 to the left and Display 2 to the right.
On Panels Window Preferences, I can select Display 1, Display 2 or set a Custom display, but no matter what I choose, including Custom with Windows Left and Top set to "0" (or any other value), as soon as I select "Show", it switches to "Display 2" and is shown on Display 2.

How can I have one panel on the left and another panel on the right, or one panel using both?

[Knaldgas]

Just tried to make the panel 3840x1080 and that is actually shown on both displays, so that works fine!

Then the remaining question is: Can I have two panels, one for each display?

[integratedcorn]

Hi, other than making the panel the larger width, did you ever find a solution so you could specify the display? I am having this exact issue as well. The panels always change to Display 2. I also have a new Pi 5 that this does not happen on.