A way to find keyboard shortcuts is to refer to the menus or in Notes. Most menu items show the equivalent keyboard shortcut to the right of the menu item or the letter of the keyboard shortcut underlined.
In Notes 8 you can use Ctrl + Shift + L (L is for Lotus I assume ?). This brings up a nice list.
Hovering over the smarticons also shows short cuts.
However this unread / read toggle using the Insert keu is NOT shown on the menu by the way.
Another usful shortcut is Alt+Enter to show properties. This useful in Notes 8 as the yellow diamond on the blue background smart icon is missing in Notes 8.