In this days there is a new open source project that basically is like the Firefox responsive view but he have the multiple view: https://medium.com/@kitze/introducing-sizzy-a-tool-for-developing-responsive-websites-crazy-fast-39a8c0061992
I think that that view can improved with that projects as reference with not so much difficult, what do you think? I have to open a ticket about it?
There have been many things like Sizzy over the years, which open the content in multiple viewports at different sizes.
Actually, the project that led to the new version of Responsive Design Mode started out as background work for offering multiple views at the same time, so it’s definitely something we’ve thought about!
There are various bugs filed, like Preview the current page in multiple window sizes at the same time and the meta bug for Multiple Viewports v1. There are various other bugs for follow on work, like keeping the viewports synchronized and crafting an inspection mode that makes sense for this.
At the moment, it’s not active project, but I hope we’ll come back to it some day! There’s definitely some exciting tools we could offer with a setup like this.
Very true but seems that devs reinvent the wheel everytime so maybe it is time to integrate that feature (multiple viewport) to have a killer feature in the browser itself 