When browsing models & scenes on sketchfab.com I like to have multiple tabs open and compare models side-by-side filling separate browser windows or tabs.
At the moment I can grab the /embed/ URL and paste it into browser tabs but it's a bit cumbersome.
YouTube kind of has this with the 'large' viewing option.
The sketchfab.com options are "in a window" or completely fullscreen, I think "fill the browser window" is a useful middle ground. Anyhow, something to consider.