It should be customisable. I had no problem adding that field to window definition.
You might try leaving only USDClass window definiton in file(+externals).
If that doesn't work, can you please provide a window definition as well?
I would like to know what BackgroundHALShouldPause does, and how to use it. While it's listed in the HAL Primitives report, it is not used in source code and it doesn't appear in the LMS HAL...
