If a signal was made with the ID inputted it will return it otherwise it returns nil.
Code Example
Operator.GetSignal("Killed") --> Nil Because no signal was made that was set to Killed
local killed = Operator.NewSignal("Killed")
killed:Connect(function()
print("OOF")
end)
----- Pretend like this is in another script
Operator.GetSignal("Killed"):Fire()