Can't be able to edit projected end date in employment history

We need to update the "projected end date" for Associates who are resuming back to work from leave early in some cases, but the option to edit it is not available in Employment History. Entering a new action to change the assignment isn’t a suitable approach, as we need to correct the "projected end date" for the current assignment itself. Can you guide us on how to enable the option to edit this field directly.