1. $notify(N).sound gives the online-sound, but either there is not a .prop to give the offline sound, or it's just not documented. If it doesn't exist, perhaps name it .offline, or if people would confuse that with the on/off status, .sound2
This is helpful for the attempt to 'theme' the ON UNOTIFY event's text display. Since /haltdef halts the on/off notify sounds as well as the text display, when theming ON NOTIFY they can check for a sound with $notify($nick).sound, but for ON UNOTIFY they'd need to parse mirc.ini to find out if there's a sound that should be played.
2. /help /notify doesn't show syntax to add/remove either of the online/offline sounds. Perhaps -o for online-sound and -f for offline sound to indicate the string isn't a note. "/notify -f nick" could be used to remove that sound without needing to delete the entry and recreate it. Or, it could stay consistent with existing syntax, where you have to delete + re-create the entry in order to change it. Switches -nof or -n or -o could indicate whether one or more strings precede the note, with the soundnames needing to be "quoted" if they contain a space. If all 4 switches are used, there's no preference to the order they should be used following the nick.
ie /notify -of nick "c:\path\onlinesound.wav" "c:\path\offlinesound.wav" note goes here
3. The /help mentions an "update" button to click on after changing an existing user's settings, but I don't see it. Unless the 'update' button is supposed to behave like an 'apply' button, perhaps it means the 'ok' button that closes the address book.
4. In the address book's 'users' tab, clicking the 'notify' button jumps to the notify tab and highlights that nick if there's already an entry in the notify tab, but just beeps if the nick isn't already there. It might be more relevant for clicking on the 'notify' button to open the 'add' dialog with the nick-box filled out, if the nick isn't already in the notify list.
5. If there's already an entry for nick 'test' at network 'test1', an attempt to add another entry for the same nick at a different network causes the prior entry to be replaced. Perhaps a dialog entry warning about replacing an existing entry with the one being edited/added.
6. As for the "use default sound" checkbox in the addressbook/notify tab, so far I've not been able to figure out how to make that do anything except play the normal online-sound, and there's no $notify().prop to show if that box is checked. I do see a section of mirc.ini like:
but it's not apparent where we can go to define a default online/offline sound.