>How to pass property array by reference with using the @ sing. Like with "Normal" arrays?

Pass the object itself.

* code in some object
This.ArrayProperty(1) = "ABC"
This.ArrayProperty(2) = "XYZ"

SomeotherObject.SomeMethod(This)
* Now This.ArrayProperty(2) = "DEF"

* code in SomeotherObject.SomeMethod
LPARAMETERS toParms
toParms.ArrayProperty(2) = "DEF"
RETURN