Um... sometimes ideas we have we should probably research and consider a little more since this idea isn't exactly new... or really all that great....

his is what I could with a desktop window manager of the stacking variety (or floating mode in AwesomeWM, or equivalents whatever they are for whatever you use), which doesn't require I use any specific set of widgets that I may or may not be able to export the data from and use elsewhere while I may or may not also have that data synced to a server that then spolls that information together and sells it to advertisers or to the government upon subpeona.

The biggest advantage possible here isn't even utilized because each window still has the bulk of the URL bar and controls on the limited viewport of the screen that here is being further divided into portions small enough to trigger mobile screen size CSS rules, which for real estate purposes should probably be universal at the top of the browser changing to the controls of the focused window like macOS' menubar at the top of the screen. This is why I have ever explored creating a browser window splitting userchrome.js script but found that for my needs, unsetting the screen width limit of "Open in Sidebar" works even better.