Comment 84 for bug 124440

I can only guess that the Ubuntu Desktop team has not been motivated to add such new configuration features because of the pending switch to Unity8.

The good news is that Unity8 frees us from the link to upstream Gnome/GTK that Unity7 is subject to. So in theory we will have more freedom to add custom configuration options more rapidly in future.

That does not however explain or excuse us for failing to add this feature in the previous 9 years since this bug was logged.