I used the example.json under sieve and created actuallyadditions.json

{
"recipes": [
{
"id": "minecraft:dirt",
"meta": 0,
"behavior": "meta_ignored",
"rewards": [
{
"id": "integrateddynamics:menrilSapling",
"meta": 0,
"amount": 1,
"baseChance": 8
}
{
"id": "actuallyadditions:itemRiceSeed",
"meta": 0,
"amount": 1,
"baseChance": 12
}
{
"id": "actuallyadditions:itemCoffeeSeed",
"meta": 0,
"amount": 1,
"baseChance": 12
}
{
"id": "actuallyadditions:itemFlaxSeed",
"meta": 0,
"amount": 1,
"baseChance": 12
}
{
"id": "actuallyadditions:itemCanolaSeed",
"meta": 0,
"amount": 1,
"baseChance": 12
}
]
},
{
"id": "minecraft:leaves",
"meta": 0,
"behavior": "meta_specific",
"rewards": [
{
"id": "minecraft:sapling",
"meta": 0,
"amount": 1,
"baseChance": 50
}
]
}
]
}

This doesn't result in the items being added. I sifted 550 dirt got all other default dirt drops but never the ones I added and the ones I added are not added to waila under dirt.

You need commas between the rewards, for example
"rewards": [
{
"id": "integrateddynamics:menrilSapling",
"meta": 0,
"amount": 1,
"baseChance": 8
},
{
"id": "actuallyadditions:itemRiceSeed",
"meta": 0,
"amount": 1,
"baseChance": 12
},...