const dados = [
  {
    title: "titulo 1",
    data: [{ a: 1 }, { b: 2 }]
  },
  {
    title: "titulo 2",
    data: [{c: 3 }, { d: 4 }]
  },
  {
    title: "titulo 3",
    data: [{ e: 5 }, { f: 6 }]
  },
];
 
// faz um loop simples, adicionando os elementos de "data" no resultado
let result = [];
for (const item of dados) {
    result.push(...item.data);
}
console.log(result);
 
// ou vai concatenando (essa é um pouco pior, pois cada chamada de concat cria um novo array)
result = [];
for (const item of dados) {
    result = result.concat(item.data);
}
console.log(result);
 

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