Apple are renowned for introducing hidden gestures that normal people don't know about but it doesn't effect their day to day use. Eg. The 5 finger pinch to multitask or double tapping on the home button in iOS.

In OSX the right click on the mouse is off by default and I regularly come across Mac users that have never switched it on. My other favourite is windows users trying to cut and paste files between folders in a single finder window instead of using spring folders.

And if you want a really hidden feature that you'd have to know about before you used it you've only got to look at 3DTouch on the iPhone 6s. That pops up a context sensitive menu whose contents change depending on how hard you press. It makes covers actions seem positively intuitive.

This could be easily solved by Jolla. Keep multiple cover actions but make them work as buttons if pressed or gestures if dragged. They do that for actions on full screen modal dialogs already - you can either click a top corner or drag the screen. Then just make the home screen navigable by edge swipes or dragging outside of covers.