Why aren't our window managers doing this?! Then it would work for all apps, and it would be redundant for chrome and others to replicate the feature internally

Why aren't our window managers doing this?! Then it would work for all apps, and it would be redundant for chrome and others to replicate the feature internally. I used to think that window tabbing and grouping was too complex a UI problem for window managers to support. The implementations I'd seen required lots of keys and buttons to control the window groups, so it wasn't worth their time to implement something hardly anyone would use. But I was wrong, of course! There should be chrome-style tab grouping everywhere.