Update:
Was able to sort this with a client script.
Example usage:
plugin.json -> { "hook": "filter:navigation.available", "method": "addNavigation" }
plugin.json -> "scripts": [ "static/lib/client-script.js",... ],
library.js addNavigation:
append the following to the hookData object:
{
route: '<some route>',
title: <some title>,
id: 'unread-count',
iconClass: '<some icon> custom-class-name',
text: <some title>
}
client-script.js:
$("#unread-count .custom-class-name").attr("data-content",<unread count>)
