A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
The direct answer to your question is that the capability has been omitted in PowerPoint 2016 for Mac. I cannot explain why it was done, but there is no available means to alter the new limitation.
Use the ☺︎ at the right end of the PPt Ribbon to add your voice to the choir. The more feedback Microsoft receives on the issue, the more likely it is to be addressed by a future update.