For some reason, chrome web store won’t load on mobile even to browse so I don’t know exactly what this extension is just yet but from the thumbnail, it appears to be the Tile tab functionality from Vivaldi.

It is one of the primary reasons I use Vivaldi alongside its ad and tracker blocker. Whenever I show people that I can CTRL + select multiple tabs and tile them like windows in 1998 they lose their mind. Then you can also stack tabs and tile the entire tab stack so that you only have one tab that shows you four websites worth of information and you could still select each individual tab.