I found Knap very interesting, so I installed it on Windows, even though I knew it was incompatible.
I verified that the processing is done successfully using pandoc. However, the problem is launching the viewer. At this point, knap shows the error Coud not launch viewer.

Analyzing Knap's launch_viewer() function, I believe that what makes it incompatible on Windows is adding the command > /dev/null 2>&1 & echo $! to the lcmd variable.
The equivalent on Windows is >NUL 2>&1 & echo $!.

Can you change this, detecting the operating system in use to run the correct command? I'm looking forward to testing it.