Updated: May 15, 2019.
With the release of our new update to ON1 Photo RAW 2019.5, we now have added support for dual displays. For more information see the knowledge base article here: Dual Display Mode
You will be able to run the ON1 programs on a machine with multiple monitors. However, all of your editing will be done on a single monitor within the program window. We do not have a feature in the Photo Raw 2017/2018 to display the image you are working on one display and the controls and tools on another. This is a popular feature request that we may be adding to the program in future updates.
We encourage all of our customers to submit feature requests to our Development team on our Photo RAW Project Page here.
We will be reviewing all suggestions and including some of these feature requests in future updates to Photo RAW.