highlights when multiple panels are aligned

when showing multiple translation panels at once highlight pointer from the master (transcription) panel leads only to a single location, cf pb-highlight/@key

<pb-highlight class="tei-seg3" id="la.1.1" highlight-self="highlight-self" scroll="scroll" key="es.1.1">
     <span class="verso"><mark>1</mark>Fraternas acies alternaque regna profanis</span>
...
</pb-highlight>