Hi,
Currently, you have implemented '%codex_total_discoveries_<category>%' and '%codex_total_discoveries%' for the number of discoveries made by the player (per category). I was also hoping you could implement something as %codex_total% and '%codex_total_<category>%' for the total amount of discoverable items (per category).
(Perhaps it would then be better to rename the placeholders as %codex_total_discovered(<category>)% and %codex_total_discoverable(<category>)%, but that would of course break backwards-compatibility... you could always make total_discoveries deprecated?)
(EDIT: fixed some formatting)