HR Organisation Chart : Showing Position as Presently occupied by other

As per our Business Practice, there are some Positions which are Vacant but occupied by some Employee as their Secondary assignment (over and above their primary assignment, which is some other position). And this position we don't want to show it as Vacant and as of now there's no plan to fill this also in near future, but as part of the Organisation Chart, we want to show this as Occupied position.

e.g. Presently in our Org Chart, CIO Position is Vacant, but we want some existing employee to appear as "Acting CIO" and don't want Vacancy report to display such positions which is dully occupied by some Employee's.

So how can we incorporate such Employee assignment to 2 different Positions, one Primary and other Secondary, so that such Positions are not shown as part of Vacancies.

Thanks in Advance & Best Regards

Harish