The reason why those are not translated is probably because they are just folders being displayed there. That makes it a bit tricky to handle it I guess.
Other OS handle similar cases in different way, none is fully satisfying IMHO. Several options:
Do not translate it at all (status quo). Pro: The application folders stay the same on all systems. E.g. you can rely on a link being put into
/boot/home/config/settings/deskbar/menu/Applications showing up in the application menu. Con: No translation, system partly not localized.
Actually rename the folders based on locale. Pro: Nicely translated folder names. Con: The paths themselves change, so you need some way for applications to get the actual path and applications must honor this. You also need to specify what happens if users change locale (should folders get renamed or stay as they were?)
Older Windows did this a lot, causing all kind of problems with applications using hard coded English path names. On Linux xdg-user-dirs handles this for some special user folders (Desktop, Documents, Music etc.). It works surprisingly well in practice there, somehow they managed to have a lot of software honor this.
Have pre-defined, English path names, but display them localized in the UI. Windows 10 does this, e.g. the actual path might be C:\Users\tim\Documents, but it gets displayed at C:\Benutzer\tim\Dokumente. Still can be horrible confusing sometimes.
IMHO for the use case presented here for localizing the deskbar entries something like the third approach might actually work. It would just handle translation of the four standard folders in the menu (Applications, Demos, Desktop applets and Preferences). If the user creates any other folder it would be shown as is. Still could sometimes confuse people if they see an Application folder when they navigate to
/boot/home/config/settings/deskbar/menu/ in Tracker, but it is shown as “Anwendungen” in the deskbar menu.
Or someone comes up with option 4: The clever Haiku way to handle this better than anyone else Unfortunately I don’t have a good idea about this myself.