@project_2501 it isn’t clear to me that the syntax arr[3, 2] does much to simplify the native arr[3][2]. As others have mentioned, the syntax arr[3, 2] isn’t possible without redefining the Java and JavaScript languages, or else adding some serious hacks to the PDE and p5.js Editor. Operator overloading, as in 5 * arr or arr1 + arr2, is also off the table without dark magic.
ND4J, TensorFlow.js, and d3-array might be good sources of inspiration for addon libraries.