You can add important and relevant topics to a group. Follow the steps below to add a highlighted topic into a group page:
Go to the groups page> Click on the (...) button on the top right> Click on the Highlight Topics> Search fo the topic and add it by clicking on it.
You will see the highlighted topics on the right-side menu:
This way, when user click on that highlighted topic from the side menu, they are able to filter the group feed based on the content which are tagged with those highlighted topics.