example.js

var state = {
  items: {
    "a": {
      location: 1,
      enabled: false,
    },
    "b": {
      location: 2,
      enabled: false,
    },
    "c": {
      location: 3,
      enabled: false,
    },
    "d": {
      location: 4,
      enabled: false,
    },
    "e": {
      location: 5,
      enabled: true,
    }
  }
}

const convert = function(obj) {
  let results = [];
  const keys = Object.keys(obj)
  Object.values(obj).forEach((item, index) => {
    item.key = keys[index]
    results.push(item);
  });

  return results;
}

console.log(convert(state.items));

output.js

[ { location: 1, enabled: false, key: 'a' },
  { location: 2, enabled: false, key: 'b' },
  { location: 3, enabled: false, key: 'c' },
  { location: 4, enabled: false, key: 'd' },
  { location: 5, enabled: true, key: 'e' } ]