GASでユーザー定義関数を使う

■Google Apps Script
https://developers.google.com/apps-script/overview

■Custom Functions in Google Sheets
https://developers.google.com/apps-script/guides/sheets/functions

■functionに複数の範囲を渡して処理する例

=myfunction(A1:B5,C1:E5)

function myFunction() {
  var arr =[];
  for (var i=0 ; i<arguments.length ; i++) {
    for (var row=0 ; row<arguments[i].length ; row++) {
      for (var col=0 ; col<arguments[i][row].length ; col++) {
        arr.push(arguments[i][row][col]);
      }
    }
  }
  return arr.join();
}