help/en-US/text/swriter/guide/word_completion.html

To Accept/Reject a Word Completion

… probably should be mentioned that ESC cancels the suggestion without requiring any characters to be typed/displayed, which may be required at the end of the line (since Enter cannot be used).

Hello
I have opted for a simpler method for the dreaded word completion. I have turned the word completion option OFF in LibreOffice settings.

Regards

Peter Schofield
psauthor@gmail.com
Technical Writer
Mobile: +48 507 930 038

although your url says “guide”, as the prefix says : it’s part of “help”,
so, feedback is expected in bugzilla : Introduction; I want to review and correct the Writer Guide as I work with Writer - #9 by Twistappel

or If you want to give a try yourself, it’s a bit tedious but doable : Editing help pages directly in gerrit - The Document Foundation Wiki