I don't think we need to differentiate between stem or root tubers but we can easily add it later if we wish. I think for stolons, those are best addressed under the propagation methods area.
I have created the Underground Structures databox and added those 5 options to it.
Now I can do mass updates. What I want to do is:
For all plants that have "Plant Habit: Bulb" checked off, check off "Underground structures: Bulb".
For all plants that have "Plant Habit: Rhizome" checked off, check off "Underground structures: Rhizome"
Then remove Bulb and Rhizome from the Plant Habit databox.
Then, I propose I go through all the "Propagation: Other methods" checkboxes and leave them alone, but any plant who has checked off Bulbs or Corms will have the appropriate checkbox checked off.
If I'm leaving anything out, please let me know!