Gibt es ein Event, das ausgelöst wird, wenn Topic-Listen neu geladen werden?

Another way is to add an observer in the topic-list component that observes topics.[] and re-runs masonry after render. i.e. something like:

withPluginApi(0.8.16, () api => {
  api.modifyClass('component:topic-list', {
     masonryObserver: function() {
        // update masonry here, probably wrapped in Ember.run.scheduleOnce('afterRender', () => {})
     }.observes('topics.[]')
  })
})