On Mac - Open Dictation by using the shortcut Command + ; (that's the command key plus the semicolon)
On Windows, open Dictation by clicking Control + ; (that's the control key plus the semicolon).
Click Settings at the top right
You can turn off a shortcut completely by pressing the checkbox.
On Mac, to change a shortcut, select it, click the key combination, and then type the new keys. The shift key cannot be used.
On Windows, we don't currently support changing a shortcut.