I have defined a widget area footer fixed like that :
Added to /nodebb-theme-material/lib/theme.js
theme.defineWidgetAreas = function(areas, callback) {
areas = areas.concat([
{
'name': 'Footer fixed',
'template': 'footer-fixed.tpl',
'location': 'bottom'
}
]);
callback(null, areas);
};
Added to /nodebb-theme-material/plugin.json
{
"hook": "filter:widgets.getAreas", "method": "defineWidgetAreas", "callbacked": true
}
created /nodebb-theme-material/templates/footer-fixed.tpl
<div widget-area="bottom"></div>
I can see a new widget area and I can put widgets on it.
But when the page is loaded and check for widget html code by the chrome devlopper tool, I can see nothing 
Any help is welcome 