Lmao sometimes I wish I knew how to code just so I could understand not only how it's difficult to take a feature that is currently implemented in one way and just change it a bit.
But that it's so difficult that it's not even worth trying
So currently we don't store the data for how many slots the player has filled in the collection log on a single variable, if we did then it would be very easy for us to do.
Each item has it's own variable on the player for how many the player has obtained, when a tab is loaded it checks against a list of items we know are part of that tab and counts how many the player has has. For simplicity sake let's take the Chaos Druids tab as it's very small only having 3 pieces.
It will do the following:
counter for total items in this log is 3, so we know it's X/3
counter for total items the player has is 0
Get the first item (robe top) if the amount is >0 increment total items counter by 1 so it's 1/3
Repeat for robe bottom and hood.
Now you could ask why we don't just count all the individual variables everytime you open the log but the sheer number of them (1300-1400 ish iirc) would be quite an expensive piece of code to run every time someone opens the log.
To make it more efficient and to display it on the hi scores version of it and to cleanly display it on the log we'd ideally want to have a new variable which tracks the total amount of unique items the player has found and this would increment every time an items variable increases from 0 to 1.
It's not that doing that is hard it's just that it would be a very very big job making sure that on the first time a player logs in after the update you check every single variable correcty, it'd also be very very time consuming to QA, not only would they have to check that no item is missed when counted they'd also have to be fairly confident that the counter increments correctly for any item the player may obtain.
It's not that our engine can't do it, it's just a bigger job than you may think and we have to prioritise which work we do and how much value that work is to the players. I can certainly see us potentially doing it in the future.