Pine's SensorML Editor
From the User Manual
SensorML Editor is a program to assist SensorML researchers to explore and modify SensorML models. It provides the functions to navigate a SensorML model in tree structure, create new model, add\delete\modify existing model and export model in XML format.
SensorML Editor is created in Java and mainly utilizes JAXB and Reflection packages. It is a general editor without hard-coding any SensorML schema. So it directly uses SensorML classes and attributes to create the model and requires user to have basic knowledge of SensorML schema. The javadoc for SensorML Parser could be a good assistant for modeling.

