How do you change a feature definition for a line you've already made?

I'm in Open Roads Designer CE 2021 - Release 2. I don't really want to create the line from scratch just to get the right feature definition, but when I change the feature definition in the feature definition tool bar it doesn't change the feature definition for the line I've selected. How do I change the feature definition for my alignment? It's a complex element, not a line, if that helps.