Review from nick on main page, from July 1, 2018, says “this version is does NOT support responsive design”.
On WebAnimator site, features listed for version 3 (the one being offered now) include:
“Responsive animations
You can design your animations to be responsive, meaning they
automatically adapt to the browser window’s dimensions.”
I haven’t tried the program yet, but at least this deal-breaker is no longer an issue :-)