Hi. I don't see a way to set a value for an additional field in a pivot table, e.g. type in this example:

static fields() {
    return {
      roleId: this.attr(null),
      userId: this.attr(null),
      type: this.attr("")
    };
  }

I prepared a sandbox: https://codesandbox.io/s/vuex-orm-sample-application-8xbyg
The data structure is actually the same that Laravel returns when you use the return $this->belongsToMany('App\User')->withPivot('type'); statement.