Duplicating placeholders on Master Slides

I am new to mac, and still trying to learn my way around.

I want to create a comparison master slide, such as I have been used to using in Powerpoint, which has One title, two subtitles, and two text boxes underneath. I want to use the existing theme as a template. I have been trying to take the title with bullet points to the left slide as my master.

My question is, how do I copy the body text placeholder in order to create an identical duplicate next to it? I don't want to start again from scratch because I would not be able to guarantee it would look the same, but I can't figure out how to simply copy and paste the whole box, I only seem to be able to manage the contents.

Any advice is welcome.

Lusule.