As far as it goes, yes, this add-on provides a sidebar displaying keywords you've prepopulated in a spreadsheet.
With regards to usablity, mm. Could do better.
First, the keywords themselves are disproportionately sized and spaced compared to the text you'd use whilst creating a document.
There's also no way to adjust the width of the sidebar, which can be quite obtrusive if you're working in split screen or on a mobile device.
This means that that any list containing eight or more keyphrases you need to use the scroll bar to view beyond the few displayed in the sidebar.
And second, a problem that compounds the oversized text/spacing issue, is there's no easy way to strike through/delete the keyphrases you've used.
You have to return to the spreadsheet, delete the line containing the keyphrase you've added and then return to and refresh the document you're working on to display the new list, minus those you've used.
In all honesty? You're no worse off creating a spreadsheet, or even a list in Google Keep, containing your keywords and have it sit adjacent to your WIP document.