I know that you normally can't change the numbers 1, 2, 3 etc. that Windows assigns to the connected monitors. At least I'm not aware of any way to do so after much research.
"Normally" referring to the case where internal processor iGPUs or discrete dGPUs and "normal" monitor connections like DisplayPort or HDMI are involved.
However I believe it should be possible to change or at least reset the numbering when connecting (several) monitors via Thunderbolt or USB-C because in that case the numbering probably is based on which monitor was connected first, second and so on.
Is anyone aware of the registry key that has to be deleted to start over with that numbering?