Sorry, Lesley, I haven't been specific enough.
I already know this usefull method to substitute a word for the translation I prefer. But this is not exactly my problem.
In fact, when I configure this custom text, I use Booking Engine> Multiple Properties> Layout, and I click on the 'Manage' button in the 'Agency Description 2' module, and then I can configure the link text in each language tab available, to expand the item or close it. I'm used to manipulate these settings for a while (for other items of course), and it usually works perfectly. And for once it is this configuration which the system does not take into account (see screenshot
https://pasteboard.co/J8bkn2x.png).
Thanks to look again at the issue !
Thierry