SUGGESTION: set_effects

{
    "pools": [
        {
            "rolls": 1,
            "entries": [
                {
                    "type": "item",
                    "name": "minecraft:potion",
                    "weight": 1,
                    "functions": [
                        {
                            "functions": "set_effects",
                            "effects": [
                                {
                                    "effect": "minecraft:speed",
                                    "amplifier": {
                                        "min": 0,
                                        "max": 1
                                    },
                                    "duration": 300,
                                    "particles": false
                                },
                                {
                                    "effect": "minecraft:mining_fatigue",
                                    "amplifier": 2,
                                    "duration": {
                                        "min": 200,
                                        "max": 500
                                    },
                                    "particles": true
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}