Add warning on some keyboard events

[lesquoyb]

Is your request related to a problem? Please describe.
When using keyboard events, there are a few specific cases:

1. in 3d display the ctrl modifier doesn't work, probably caught by the display to manipulate the view.
   

2. the command modifier is not available on other operating systems than macos
   

Describe the improvement you'd like
I propose that we add a warning at model validation when in those cases

Describe alternatives you've considered
For the command modifier we could also add a general super modifier that fits command/windows key to be cross platform