I tried to blacklist some items and it did not work. did I do it correctly? It looks like this:

"blacklisted_items": [
"minecraft:amethyst_shard",
"minecraft:netherite_sword,
"minecraft:minecraft:diamond
],

that's completely wrong, please use a JSON compatible text editor like VSCode or sublime text.

You're missing the final quotes on the 2nd and 3rd entries