The idea of improving discovery is awesome. People discover everything, even when some teacher has to rub their nose in it to help them discover what they're discovering.
I've always had trouble discovering what the control-keys are at the moment. Apparently people think tooltips are just for icons, go figure, but i've never hit Ctl and seen a popup listing the next-key possibilities like command completion. User-interface experience-level settings are feasible in order to give newbies the help they need without getting in the way of those who aready know this or that.
There is so much that can be done, but i think it's important to create some universal starting-point, so that if people can remember how to get to that "home" state, they can easily find all the rest of it again.
In these forums the "home" place is always available by clicking the mate-symbol top-left. In Ubuntu-MATE maybe it's the Welcome app, and if there's a universal something-or-other... icon, control-key, whatever... even newbies can see how to quickly reach the place where they can find out how to do what they want to do.
In boxed-set days linux had lots of problems, and most of those have gone away. But it's still missing something in terms of being a unified whole instead of a warehouse of parts. Today's "control panel" app is vastly improved over what was available even a few years back. The welcome app is great, but i think its functionality might be better expressed as a little more than just welcoming; welcoming is fine, returning home maybe better.