As discussed here: Use two Mac apps side by side in Split View - Apple Support
It would be great if we could use split view on macOS as we do on iOS w/ iPad.
In macOS that’s just a matter of arranging your app windows. Has been around since day one…
Examples:
There are a ton of benefits to actual split view support like persistence across multiple desktops that window arrangement doesn’t support.
Also - I would note that you’re unable to resize the player outside the bounds of the media aspect ratio, so even a tool like moom would only work for library views.
Why would you want to mess with the media aspect ratio?