@Forferdeilig: It seems that the devs didn’t find it a useful feature. Luckily, there is a workaround.
Move all the objects you want to make appear or disappear together on a separate layer.
Then in the Layers tab, add the layer to the Exclude list to make the object disappear, or deselect it to make the object appear. That is much easier to keyframe. Only one item.
As for the visibility, work also with the layers. Select or deselect the layer here or at the bottom of the viewport. Use [SHIFT LMB] in order not to alter the state of the other layers. (This is just to make the viewport cleaner. The state of the layers can’t be animated… any more.)