Hello, Eunbyul.

Thank you for the shared details. I am happy to hear that you managed to implement the desired functioanlity in your application. I will now close the current thread but if you need further assistance, you can reopen it and continue the communication. 

Regards,
Petar
Progress Telerik

Hello, Eunbyul.

After investigating the reported issue, I can share that it is triggered by a missing property in each of the objects, part of the array passed to the Grid's columns. The property I am talking about is the orderIndex. If we add the marked in yellow line in the reorderColumn method, the reordering functioanlity is working as expected:

const reorderColumn = (event: GridColumnReorderEvent) => {
  // event.columns doesn't include hidden field.
  const [prevField, nextField] = [
    event.columns[event.prev].field,
    event.columns[event.next].field,
  ];
  const prevIdx = columnList.value.findIndex((el) => el.field === prevField);
  const nextIdx = columnList.value.findIndex((el) => el.field === nextField);

  const el = columnList.value[prevIdx];
  columnList.value.splice(prevIdx, 1);
  columnList.value.splice(nextIdx, 0, el);
  columnList.value.map((el, index)=>el.orderIndex = index);

  emits('updateColumns', { columns: columnList.value });
};

As I couldn't load the shared project, I copied it to a local one. Attached to my reply, you will find the mentioned local project in which the discussed above line is added. 

Please check the attached project and let me know if it helps you implement what you need in the application you are working on.

Looking forward to your reply.

Regards,
Petar
Progress Telerik

Hello, Eunbyul.

Thank you for the shared details about the experienced issue. Before we can confirm that the reported issue is a bug we will need to do some additional research about your scenario. 

I will write you back withing the next up to 24 hours with an update regarding the current thread.

Thank you for your patience and understanding.

Regards,
Petar
Progress Telerik