John,
The news isn't good, but at least it is not a total loss.
You should be able to add extension points now. Right-click the use case in question, and from the context menu choose Advanced | Edit Extension Points.
However, if you mean that EA should detect these and add something to the notation or graphic automatically, then EA is lacking here; you have to do this manually. Note that many some authors are depreciating display of extension points in favor of using «extend» links. Still, your point stands, and this could be useful in some approaches to transformation scripts and automation support.
As to the whole business of highlighting references to actors or other use cases (or anything else for that matter), this would require formatted Notes text. This is a long-standing feature request. Lately, this seems to be getting some traction, and Sparx may have it on their wish list. As of build 801 (802 is current at this time) we've been able to display a Notes compartment on some elements, so formatting could well be on the way.
Once we have the ability to format the Notes field, highlighting becomes possible.
Here's two suggestions you might want to follow, which could help move this along. Please take a moment to look through the Suggestions and Requests section of the forum for the most recent thread requesting rich text (or whatever) formatting in Notes. Take a moment to post a message adding your support. This helps Sparx gauge the level of interest in a given requests, so they can prioritize development.
Once there's movement - or perhaps right away - you could start a thread requesting automated highlighting of names of elements linked to the use case. Perhaps you might even suggest (I shamelessly hint) that we could add a link via some kind of dialog and have EA insert (and highlight) the name automatically. That way perhaps EA could update the Notes field if the name changed. Wow!
HTH, David
