This worked perfectly. Using the development branch for my NodeManager library and changing my 'void before()' to the following code presented the proper unit_of_measurement to my Home Assistant controller for the pressure sensor. Thanks for the assistance.
void before() {
/**********************************
* Configure your sensors
**********************************/
// send unit prefixes to controller (i.e. V, A, hPa, %, etc.)
nodeManager.setSendUnitPrefix(true);
// let controller know ambient pressure sensor reports in hPa
ambient.children.get(3)->setUnitPrefix("hPa");
// report ambient measurements every 15 minutes
ambient.setReportIntervalMinutes(15);
// report battery level every 60 minutes
battery.setReportIntervalMinutes(60);
// report radio signal level every 10 minutes
signal.setReportIntervalMinutes(10);
// only a pseudo SR_TX_RSSI and SR_UPLINK_QUALITY are available for NRF24
// radio. All other methods return as INVALID.
signal.setSignalCommand(SR_UPLINK_QUALITY);
// call NodeManager before routine
nodeManager.before();
}