Reactive power can be recorded using a formula register.
First, create a power register for the equipment monitored:
Next, click the power sub-type selector box to the right of the "P" box:
Choose "* Record apparent power" and press OK:
Finally, add a new register, change the "P" box to an equals sign for a formula register, choose "react. power [var]" as the unit, and enter a formula of:
where registername is the name of the power register. Note the asterisk (*) on the end of the second register name, this references the apparent power register.