Seems strange to me, but looks like Cinema 4D doesn’t have ability to show total polycount in scene.

However we can do it at least this way:

If you want to know the total number of polygons in your scene then you need to bring up the “Project Information”. Object Manager > Objects menu > Project Information
Or by pressing CTRL + i

additional info:

Even after I am tagging the ‘Total polygons’ in the HUD tab of the Viewport, it does not display this data (unlike the ‘Total objects’).

You have to be in polygon mode for the HUD element to be visible.

That’s because you haven’t got a polygon object or objects selected. Try this: Create a cube and make it editable. Go into polygon mode. You’ll then see the HUD element saying 6 polygons. It displays the total number of polygons for the selected object or objects.

It also exist a plugin called Budget

Links:

https://www.c4dcafe.com/ipb/forums/topic/85502-total-polygons-hud-display/

Budget plugin:

http://www.biomekk.com/index.php?itm=13