A RAR can be delegated to another user when the reviewer is unavailable. The delegate is only for the current RAR and does not affect other RARs in the series.
To delegate a RAR, click on the three-dot menu then "Configure Current RAR".
Click change and select the new reviewer that will delegate the RAR.
A delegated RAR will show the delegate's initials next to the date of the RAR in the dropdown.