Unlike the encounters table file, the drop rewards is not fixed to specific number items for each and every Pokemon in the encounter table (the array size of the data block may even be the only limit but unlikely.) The perfect example of this is the New Year's Magikarp event where Magikarp rewards had more slots than the other Raids at the same level in the lower Star levels. However, it seems like it would be the best for narrowing down the structure as the rewards for Magikarp were pretty much just: Nuggets & Big Nuggets.
I assume the structure is: Header than a sub-array of items:
Item ID | Drop Percentage
There is likely a header for each sub-array which serves as an ID value. I imagine this portion corresponds to the normal_encounters file!
Due to the cheats scene, these are the only Gen 8 hex values I know for items:
Masterball | 01
Ultraball | 02
Greatball | 03
Pokeball | 04
Safari Ball | 05
Rare Candy | 32
PP Up | 33
Zinc | 34
PP Max | 35
If someone happens to have the item id values for Big Nugget and Nugget, it would be helpful.