I have right clicked on the toolbar but nothing in the drop down menu says anything about adding subdocks. Is there a way to stack the icons into subdocks in the free version?

No, despite the free version already being much more powerful than it should for its own sake (I need to eat too lol), it does not support sub-docks.

With Nexus Ultimate or Winstep Xtreme, on the other hand, you can have as many docks and nested sub-docks as you want, tabbed docks (shelves), drawers, grid stacks, launch pads, more modules/widgets and effects, and a ton of other stuff that is only available in the paid versions.