Would I use markers or elements?
In unstructured mode, all you can do is pick up the entire content available in the <$paratext> building block. There is no marker text available.
You can kludge this by creating an anchored frame with a text frame that holds the desired text of the cross-ref that must use a unique paratag that has a colour attribute that is set to be invisible in the Color View mode used during the publication step. [Set the Aframe to outside the column or text frame so that it doesn't visually affect the appearance of your content flow.]
In structured mode, IIRC, you need to wrap the desired text in a separate element.
In an unstructured document:
In a strucured document: