Steps:

1.Left-click on one of the tasks of the operation you want to move.
2.Hold down the Ctrl key and press arrow keys.

Right arrow key
Moves an operation to the right. If you move the operation to the rightmost column, you cannot move the operation any further.
Left arrow key
Moves an operation to the left. If you move the operation to the leftmost column, you cannot move the operation any further.
Up arrow key
Moves the selected task to another candidate resource above the current resource. If you move the task to the top of the candidate resources, you cannot move the task any further.
Down arrow key
Moves the selected task to another candidate resource below the current resource. If you move the task to the bottom of the candidate resources, you cannot move the task any further.

When you move an operation using the keyboard, the operation is moved according to the step specified for the property “Operation move step”.
Also, if you move an operation by pressing arrow keys while holding down the Ctrl and Alt keys, the operation will be moved according to the step specified for the property “Operation move step (ALT)”.
If the selected task or operation is unselected or if you perform some other action after selecting a task or an operation, you will not be able to move the task or operation using the arrow keys. In that case, select the task or operation again using the mouse.