I’m not sure how possible it is to add tabs to the journal via modding (others are more knowledgeable there) but it’s definitely possible to extract all game text from the files and put together something viewable outside the game, which is a bit more extreme than having a running log of only the conversations a given character has personally had interaction with.
I would also note that ALL text is already available outside of the game.. provided to the community for translation purposes..
…however, that isn’t exactly in the most “readable” format.
Also notable is that someone already .epub/.pdf’ed all the game’s lore notes for easy reading…