Taking a screenshot on my tablet requires pressing 2 buttons simultaneously. If they’re not pressed together you either
a) turn the device off or
b) turn the volume up.
Taking a screenshot on my phone requires pulling down a menu and selecting an icon. If you don’t catch the menu right it opens an alternative, different menu that can’t take a screenshot.
Taking a screenshot on my laptop requires pressing 1 button.
Choosing to make something mobile might mean it’s less accessible. Don’t overcompromise.
Lost and Desperate 
There is also the issue of what device your trainee is using. What works on yours might not work on theirs, or the methodology – combination of keys required – might be different.
Like people, gadgets aren’t all the same.
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You can also (on android e.g.) ask your google assistant to “take a screenshot”. Might come in handy some time.
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