<Celll
  v-for="(col, colIndex) in columns"
  :key="colIndex"
  :col="col" // add this
  :row="row"

<script>
import { h } from 'vue';

export default {
  props: {
    col: {
      type: Object,
      required: true,
    },
    row: {
      type: Object,
      required: true,
    },
  },
  render() {
    return h('td', null, this.col.children.defaul(this.row));
  },
};
</script>