I think simplest way just use invoke code activity.
But for my opinion it’s not worth it. Using optimized way of copy array elements in RPA projects I think its just overkill. We wait 1 second for some button in UI and for this time you can uneffective combine I think million arrays together.
If I need combine array I would use LINQ operators. Because they self explanatory. For example,
a,b, c array of something.
c = a.Concat(b).ToArray - c contains both elements a and b.