Here is a sample code to combine OBX-5 and remove extra OBX segments
var obx5Values = source.getAllNodes('OBX-5');
var newObx5Value = '';
for (var i = 0; i < obx5Values.length; i++) {
if (i !== 0) {
newObx5Value += ' ~ ';
}
newObx5Value += obx5Values[i];
}
message.removeAllNodes('OBX');
message.setNode('OBX-5', newObx5Value);