I wanted to do the same, but also haven't found any software to do it yet, so in the end I just used Tools >Settings >General >Own Key to assign HandyDiary to MyKey and also used Tools >Settings >General >Standby >Shortcuts to assign HandyDiary to one of the shortcut keys on the phone front.
It does the job, but I would still be keen to find ways to reassign the other shortcut keys inside as well though!