I just found the Keyboard Shortcuts control for the first time, and I was genuinely confused by the terminology in it. It took me a while to figure out what "New accelerator..." meant when I clicked on toggle fullscreen mode to give it a new shortcut, and then I had to read the explanatory text below a couple times to realize that "keyboard shortcut" and "accelerator" mean exactly the same thing.

For consistency's sake, we should just get rid of the term "accelerator" entirely, and replace the text with:
"To edit a shortcut key, click on the corresponding row and type a new key combination, or press backspace to disable the shortcut."

When you click an entry instead of "New accelerator..." it should instead show something more obvious, like "Press new key combination"