No, you can't, and it makes no sense honestly to have a feature like that.
If you need to dynamically assign some data with key and value, you could use an dictionary:
Dictionary<string, RectangleShape> shapes = new Dictionary<string, RectangleShape>();
shapes.Add("matrix1_2", new RectangleShape( ... ));
Then you can simply read the "variable" like
shapes["matrix1_2"]
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