Feature Request: Prevent duplicate word entries

[FenwayFrank]

Feature Description
A clear and concise description of what your feature is / does.

Prevent a word that has already been entered in a previous line from being reused, either by highlighting the word in red in the same way a non-word is treated and perhaps highlighting the row that is being duplicated.

Motivation
A clear and concise description of why you think the feature would be beneficial.
I’m really clumsy with the keyboard today, hitting the “enter” key before noticing that I typoed on a word that I was trying to enter.