(Sorry to necro a post, but I figured if people are still looking for this info I might as well give what I know.)
I looked through the indiana binary (Spacer's Choice edition) in GHEX to find all hardcoded keys because I play games with ESDF for movement, and a lot of other keys on my 24-button mouse (including IJKL for things like melee), so I'll list them all below.
Do the same steps for these as what Sebastony explained above (AddedActionKeyBinds and RemovedActionKeyBinds).
VIEW LEDGER: ActionName="ToggleLedger" (note: Oddly you can't remove Tab from this, but you can add a key and it will show up as a Secondary keybind.)
VIEW INVENTORY: ActionName="Inventory"
VIEW CHARACTER MENU: ActionName="CharacterSummary"
VIEW JOURNAL: ActionName="QuestLog"
VIEW COMPANION MENU: ActionName="Companions"
VIEW MAP: ActionName="LedgerMap"