The "Ctrl++" default is a bit weird - because there is no "+" key,
this is in effect a "dummy" binding (does nothing), but to allow for
users changing the defaults it must still bind to the actual Zoom In
function. If a user changes this key binding, then there is no way
they can change it back to Ctrl++ other than by resetting it to its
default (it is not possible to type Ctrl++ due to the absence of a "+"