#2169 Show keyboard shortcuts

[Vasco]

One of the powerfull features of freeplane are the keyboard shortcuts. However, it is very hard to learn them now.

It would be very helpfull if keyboard shortcuts are shown:
- in all menus, including the right-click context menus.
- in the tooltips for toolbar buttons

Furthermore it is not possible to find the hot-keys map (in the help menu) in the documentation maps.

[sensor66]

I also ask for this feature.