The grimoire/lore for example. The same way we have record books would have been easy to keep a literal in game record of all the grimoire and audiofiles. Horizon Zero Dawn does this very well. Every journal or audiofiles you discover is out into your folder you can go back and reread or listen to each one. It's a literal collection that your character keeps. I'm honestly shocked that Bungie didn't think to do that. That way we could also have something to grind for like the dead ghost/ chest hunt.
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Simple solution. Use one of the MANY (oh so many) unused doors in the Tower and add in a library archive. A room with computers and monitors, with the Cryptarchy working tirelessly. Make a few terminals to interact with for different categories and make it fill as we complete activities and play the game. Categories could be for enemies, factions, vehicles, weapons, armor, locations, etc..