appId in different templates

I have “appId” in my template “tasktemplate” but how do I get the “appId” so I can use it in my other templates e.g “category” template

Router.route('/tasks/:_id', function() {
this.render('tasktemplate', {
    data: {
        appId: this.params._id

I just need to get the task id so i can use it different placers on my app (navigation, footer…)