- Edited
Just wanted to add some things to what has been said
There is no concept of button folders that I recall in browsers.
Overflow menu as you mention kinda is, so i guess the idea is just multiple overflow menues with custom selectable icons
they are better represented by text, because you might not remember the icon.
I think its a valid point tho, that if you have a huge amount of buttons text is a better way, but I kinda feel like thats an argument for folders, here is a sketch which is basically like overflow menu, so it includes tittles of each button: