muk_web/muk_web_theme/static/src/xml/sidebar.xml

<?xml version="1.0" encoding="UTF-8"?>

<!--     
	Copyright (C) 2018 MuK IT GmbH
	
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of the
    License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>. 
-->

<templates id="template" xml:space="preserve">

    <t t-extend="Sidebar">
	    <t t-jquery="button" t-operation="replace">
            <button t-if="section.name != 'buttons'" data-toggle="dropdown" aria-expanded="false"
            		t-attf-class="o_dropdown_toggler_btn btn btn-secondary dropdown-toggle #{section.icon}">
                <t t-if="section.name == 'files'" t-raw="widget.items[section.name].length || ''"/>
                <t t-if="!section.icon" t-esc="section.label"/>
	        </button>
        </t>
	</t>

</templates>