Allow "Alt" key and "Super" key for key-combinations; set default key-combo to toggle between modes

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I am using a non-Japanese keyboard, therefore there are no dedicated keys to toggle between input modes (i.e. direct input, hiragana, katakana etc.).

On Linux (Ubuntu 24.04) the default key to toggle IMEOn/IMEOff is mapped to the physical japanese keys only. As a user one can set a custom key-combination to toggle IMEOn/IMEOff, but this is not set as default

Feature Request 1: Add (default) additional key-combination to IMEOn/IMEOff, so that users don't have to set it themselves and that works among various keyboard layouts (i.e. MS IME uses Alt + ` (Gravis))
Features Request 2: Several keys are not recognized. I.e. I cannot set any combination with Alt, AltGr and Menu key