What about putting the tag in the keywords column instead? It is hidden off-screen but is used for additional search terms. We are already having issues with the width on some mobile devices so the extra column could make things worse.

As for what should be the French, I'm not sure what you are precisely meaning by tag in English and there are multiple translations for the word tag. I'm not sure "Tag" for a title would mean anything to others. If you are meaning more like a keyword or an identifier then this column should be merged into the keywords column instead.