This may be repetitive, but at the very least it could be useful for someone.

I have mapped each ability to its entry in the Character>PlayerData>PlayerCustomData>PlayerUpgrade category. It appears the format is just a 32 entry array, with 3 or 4 empty elements.
Click to reveal..

{Man-at-Arms, Marksman, Scoundrel, Single-Hand, Two-Hand, Tenebrium, Bow, Crossbow,
Shield, [Unknown], Armour, Witch, Telekinesis, Willpower, Pyro, Hydro, Aero, Geo,
Blacksmith, Sneak, Pickpocket, Lockpick, Loremaster, Craft, Barter, [Unknown], [Unknown], [Unknown],
Charisma, Leadership, Lucky, Body Build}
I have no idea what the [Unknown]s are, but I believe the last three are just for spacing so that it stays in a power of 2 size. The first one seems to be some form of armor, but I haven't seen any yet.