Well I don't handle any dejure assignment in landed titles anyway, it makes it a nightmare to update it i mostly just dump all my own titles at the end and use the history files to add them to the game.You can have as many files as you want. Note that if you want a title to be under another title, all titles involved need to be in the same file.
So how do I do just add a text file called "more_landed_titles.txt" to the landed titles folder?