RailClone does not keep any reference to the library, once the style is selected. The segments and parameters are embedded in the object.
If you need to modify a segment imported from the library, please try this procedure:
1) Create a RailClone object using the library style.
2) Select the segment, and click "Extract current segment" icon. This will create a new object in the scene with the segment's geometry.
3) Now you can modify the segment's mesh, the changes will be reflected in RailClone.
4) If needed, use "Geometry->Copy To", to apply the new style to other RC objects, or save it to the library.
If you modify the segment, all RC objects that use the same style (applied with Copy To) will be updated properly. You can also remove the segment's object from the scene when you're done (RC keeps a internal reference to it), and repeat the "Extract" procedure if necessary.
Note: i just realized would be useful a "Copy To" massive option, to apply the style to a list of RC objects. We will add this feature.