(1.18) How to use it.

• Create a datapack
• create folder effects under x modid data/modID/effects
• add a json file for x block like this

{
  "block": "minecraft:dirt",
  "effect": {
    "potionName": "minecraft:slowness",
    "strength": 0,
    "duration": 100
  }
}

btw duration is in ticks!

add "enabled" : false to disable existing block effects.