If you are using another plugin to set common events to certain keys, then this plugin won't work -
"Probably not compatible with plugins that assign common events to certain key presses."
For custom keys, this plugin "at this stage only can assign your own keyname to reference to in script calls."
So at most you can check if a custom key is being pressed with script calls - (see the inputs section here https://docs.google.com/spreadsheets/u/0/d/1-Oa0cRGpjC8L5JO8vdMwOaYMKO75dtfKDOet...
What you can do with it depends on what you do with these script calls.