Under a group's settings > Content > 'By Default, display the following type of item on the group page'. Have the option to select more than one type of item for the group to see.
Currently you can only select one type of item, in my organization we use multiple types. I'd like to hide the feature layers from the groups since viewers don't need to see those, they are in a map or app. Therefore, I either have to select one type, running the risk of excluding certain items or I have to select 'All' then running the issue of having people see everything (like feature layers) and can lead them to getting confused and viewing the wrong info or losing the effect of the map created. Most non-GIS people don't always remember the difference between a feature layer and a map and click the wrong thing.