It doesn't seem useful to everyday computing but I imagine there are niche scenarios where it could be valuable. Stenography comes to mind, or perhaps some mach

It doesn't seem useful to everyday computing but I imagine there are niche scenarios where it could be valuable. Stenography comes to mind, or perhaps some machine control or clerical application where there are a limited set of input words that are valid and free typing is rare or disallowed. A "sticky" modifier key (like caps lock, num lock, etc) that enables or disables it would vastly increase the value in a general situation though.