Key commands are defined in the "Key commands" window in Nuendo. These commands are stored in the corresponding "Key Commands.xml" file, and that file is read by the plugin.
If multiple versions of Nuendo are installed on the computer, the plugin will automatically read the file for the highest installed Nuendo version (see Advanced configuration if you want to use another version of Nuendo).
The plugin will in real time keep track of changes made in the file. If you add a key command in the Nuendo configuration, it will immediately be available for selection in the plugin. If you change the actual key for a command already used by the plugin, the plugin will immediately adapt to that change and send the correct key command.