You could go with something like Eingabentastenumschalteverwechslungsangst, if you enjoy needlessly long compound words. Doesn't mention newline or messages, though. Sendetastenverunsicherung is a bit looser and closer to something someone would actually use.
@peter_sc @spiralganglion a little bit shorter but more to the point: Zeilenabschlussunsicherheit - i think it captures this particular moment quiet well and it's a beautiful German word.
Literal translation for non Germans: the uncertainty (Unsicherheit) of how to terminate (Abschluss) a line (Zeile).
@_tillwe_ @peter_sc @spiralganglion would also be a legit translation.
I always associate Verunsicherung with the great Austrian satirical 80ies Pop Band "Erste allgemeine Verunsicherung" (EAV), that's why I am avoiding the word.