This feature was introduced in v15.00. The release notes are a bit cryptic…
… so I created some examples to help me understand how these work. Here’s a screenshot, but it will be easier to read if you get the model “Topological references via underscores.ebs” on my Ebsilon Tips OneDrive.
Applications
This can be useful in Text Fields, or EbsScripts if you need to refer to, or “travel along” the topology (i.e. a string of components and pipes).