Objects that can't be grouped in PPT 2013

The majority of objects can be grouped in PPT, pictures, charts, shapes, textboxes etc...

Yet there are some objects that cannot be grouped:

Tables
SmartArt
Placeholders (see slide master)

Have a look at these previous blog articles that discuss the same issue:

Can't group two pictures
and
Grouping with a content placeholder

Attention
The trick with copying the placeholder to overcome the problem does not work any longer in PPT 2013.