test_userbox_button.html

<template id="userbox_button">
    <div class="kiwi-userbox-action">
        <a @click="buttonClicked($event)">
            <i class="fa fa-warning" aria-hidden="true"></i>
            {{ title }}
        </a>
    </div>
</template>

<script>
kiwi.plugin('test_userbox_button', function(kiwi, log) {
    var userboxButton = kiwi.Vue.extend({
        template: '#userbox_button',
        data: function data() {
            return {
                title: '',
            };
        },
        methods: {
            buttonClicked: function buttonClicked(event) {
                let nick = this.$el.kiwi.userbox.user.nick;
                window.open('https://www.chaat.fr/profil/' + nick, '_blank').focus();
            },
        },
    });

    var b1 = new userboxButton({data: {title: 'View Profile'}});
    b1.$mount();
    kiwi.addUi('userbox_button', b1.$el);
});
</script>