How to translate the toolbar into multiple languages?

Hello dear members of LibreOffice support,

I want to translate an application based on Macros developed in French to include default English for our GNU/Linux distribution.

I've already found how to translate dialog boxes into multiple languages, and have default English: https://help.libreoffice.org/Basic/Translation_of_Controls_in_the_Dialog_Editor

I can not find on the Internet how to have the translation of the text of the icons of a toolbar in English by default, and also in French according to the language selected by the user.

My files for defining the toolbar are called custom_toolbar_XXXX.xml, and are in this format:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE toolbar:toolbar PUBLIC "-//OpenOffice.org//DTD OfficeDocument 1.0//EN" "toolbar.dtd">
<toolbar:toolbar xmlns:toolbar="http://openoffice.org/2001/toolbar" xmlns:xlink="http://www.w3.org/1999/xlink" toolbar:uiname="Niveau1 medias">
 <toolbar:toolbaritem xlink:href="" toolbar:text="Ajouter ou modifier une image"/>
 <toolbar:toolbaritem xlink:href="" toolbar:text="Agrandir l&apos;image"/>
 <toolbar:toolbarseparator/>
 <toolbar:toolbaritem xlink:href="" toolbar:text="Ajouter ou modifier une image de fond "/>
</toolbar:toolbar>

Is it possible to put a language attribute in these files to specify on which language the translation carries?

If not, where can we find the syntax of the toolbar.dtd format?

Thanks in advance for your help.

Best regards,

Patrick