Multiple modifier layers with XKB (on a japanese keyboard)

I have the following keyboard (HHKB JP).  I'm using Lubuntu 14.04, and I've edited /usr/share/X11/xkb/symbols/us to implement a [custom layout](http://mkweb.bcgsc.ca/carpalx/?full_optimization) . Now, I want to use the following keys as 5th, 6th, 7th, ..., and 20th level modifiers. (On Windows, I accomplish this with AutoHotkey, and now I can't live without (at least some of) them.) I have 2 problems. 1. I don't know what the "names" for some of the non-standard keys on the keyboard (in order to add them to /usr/share/X11/xkb/symbols/us). 2. I don't know how to add extra modifiers with xkb (I understand xmodmap is deprecated), specially "normal" keys like 9. My questions are: 1. How do I figure out the names/codes for the mystery keys (eg. key )? 2. How do I add an arbitrary number of modifier layers to any given key? Note: perhaps this cannot be accomplished with XKB. I'd be delighted to know of some scripting tool that can implement this.