Use the Help option to display a help page for the toolbar options.
The json file for this help text is in the \assets\resources\<language> folder in the Magellan engine.
Do not modify the Magellan engine json file. Instead, add a copy of the file to <your theme name>\assets\resources\<language> folder and make changes. The theme file is used on book publish.
Each language json file must be updated separately, using the same process.