Can't you simply do that? (But then you would have to do that for every creep type).
Troll Drops
Events
Unit - A unit owned by Player 6 (Orange) Dies
Conditions
Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
Or - Any (Conditions) are true
Conditions
(Unit-type of (Dying unit)) Equal to Troll Worker
And - All (Conditions) are true
Conditions
(Owner of (Killing unit)) Equal to Player 1 (Red)
Then - Actions
Set animaldrops[1] = Bone
Set animaldrops[2] = Bone
Set animaldrops[3] = Troll Worker Mask
Set animaldrops[4] = Troll Mullet
Set animaldrops[5] = QuilBeast Pelt
Set animaldrops[6] = Troll Worker Mask
Set animaldrops[7] = Troll Worker Mask
Set animaldrops[8] = Troll Mullet
Set animaldrops[9] = Troll Skull Spear
Item - Create animaldrops[(Random integer number between 1 and 12)] at (Position of (Dying unit))
Else - Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
Or - Any (Conditions) are true
Conditions
(Unit-type of (Dying unit)) Equal to Troll Hunter
And - All (Conditions) are true
Conditions
(Owner of (Killing unit)) Equal to Player 1 (Red)
Then - Actions
Set animaldrops[1] = Bone
Set animaldrops[2] = Bone
Set animaldrops[3] = Troll Axe
Set animaldrops[4] = Troll Mullet
Set animaldrops[5] = QuilBeast Pelt
Set animaldrops[8] = Troll Mullet
Set animaldrops[6] = Bone
Set animaldrops[7] = Troll Mullet
Set animaldrops[9] = QuilBeast Pelt
Item - Create animaldrops[(Random integer number between 1 and 14)] at (Position of (Dying unit))
Else - Actions