It should work fine if you add it manually.

Weapon Damage Scaler
Allows scaling of player damage per weapon/ammo/skin/prefab
Total Downloads: 1,411 - First Release: Jan 3, 2016 - Last Update: Dec 4, 2017
Allows scaling of player damage per weapon/ammo/skin/prefab
Total Downloads: 1,411 - First Release: Jan 3, 2016 - Last Update: Dec 4, 2017