In large IMX files, it is helpful to document parts with comments.
Comments always start with <!-- and end with -->. In between may lie a few comments, but also entire sections.
<!-- This is a comment line -->
<!-- The following objects are disabled by comment
<mo name="Valve_1" typeClass="ModularSystem.Function.Valve"/>
<mo name="Valve_2" typeClass="ModularSystem.Function.Valve"/>
<mo name="Valve_3" typeClass="ModularSystem.Function.Valve"/>
-->