If you click on 'Webmaster Mode' in your X-Cart admin, adn then 'Open Customer site in Webmaster Mode', you will see all editable language variables show as green text. If you double click on any of these language variables, you will be able to edit them on the fly.

If you prefer to edit the language variables one at a time, you can open 'Languages' and find each variable you want to edit.

Aha ... now that sounds VERY interesting indeed. I missed 'Open Customer site in Webmaster Mode' This I must see ... Thank you.