import * as wjcGrid from "@grapecity/wijmo.react.grid";
(...)
 const [test, setTest] = React.useState(true);

  const columns1 = [
    <wjcGrid.FlexGridColumn header="test 1" binding="test1" key={0} />,
    <wjcGrid.FlexGridColumn header="test 2" binding="test2" key={1} />
  ];

  const columns2 = [
    <wjcGrid.FlexGridColumn header="test 3" binding="test3" key={3} />
  ];

(...)
 function changeTest(s) {
    setTest(!test);
  }


return (
    <div className="App">
      <button onClick={changeTest}>변경</button>
      <div className="container-fluid">
        <wjcGrid.FlexGrid
          autoGenerateColumns={false}
          ref={grid}
          itemsSource={source}
        >
          {test ? columns1 : columns2}
        </wjcGrid.FlexGrid>
      </div>
    </div>
  );

const grid = React.useRef();
(...)
function removeColumn(){
    if (grid.current.control.columns.length >= 2) {
      grid.current.control.columns.removeAt(0);
    }
}