Hello, I have a mod and I want to implement a quest system. I am going to have well over 200 quests, but the issue is that I need a way to keep track of the items the player has acquired or the task that he/she has done far, so the first thing I thought of was NBT. Then I realized that one it may be a bit chaotic keeping track of it when the player dies and two I heard that having too may NBT tags loaded on every player may cause a lot of lag and very large file sizes. So I need suggestions on how I could make a system in which I could store a ton of data on quest.

Just make your storage classes serializable and store them on the server.