How would I find the amount of nbt data an item in my singleplayer minecraft world?

I am trying to save a bunch of items I have for various reasons by placing them in a singleplayer world. This serves the purpose of backing it up (I have most things in saved toolbars) and reducing lag from opening the saved toolbars tab. My problem is that if too much nbt data is in a single chunk, it kicks me and the chunk won’t save. This has happened before, but so far I am able to give each of my saved toolbars their own chunk without any problems. This is annoying because the more items I have, the more effort it will take to get the stuff.

I tried downloading nbt explorer, but I haven’t figured out how to check the amount of nbt data (in bytes because chunk banning could be an issue) an item/items has. Is there something specific I need to do in nbt explorer? Is there a separate external tool that might be more useful? Also I don’t remember the exact limit and can’t find it with just a google search. Is there a better place to post this?