It kinda is. Across most Google products it is (gmail, music, calendar, etc). Most hotkey JS libraries I've seen also use ? as the default for seeing all of the

It kinda is. Across most Google products it is (gmail, music, calendar, etc). Most hotkey JS libraries I've seen also use ? as the default for seeing all of the bound hotkeys, so anyone who uses a library should have it by default too. It's always the first thing I try on a website.