@lebout2canap Hi! Try asking on https://ask.libreoffice.org with details about your setup (LibreOffice version and operating system) and someone should be able to help 😊
In LibreOffice, in the "View" menu, when "Field Shadings" is checked, non-breaking spaces (NBSP) appear grayed out, but narrow no-break spaces (NNBSP) do not. Is it possible to make narrow no-break spaces appear grayed out as well? And if yes, how ?