My browser (Seamonkey) has Edit>Undo right in the top bar. That's what I use. I guess the more modern browsers everybody loves hide everything from a user for a "clean" interface. I can also select text, right click, and delete from a dropdown menu of commands in my flavor of Linux.
Might be possible to alter the interface theme for whatever browser you are using to make it more amenable to user controls and tools. This site isn't the only one where being able to edit input easily is an advantage.
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