HABPanel navigate URL from string


Over the last days I created an esp32 based piece of hardware to communicate with the interphone of my flat (the place is rented, so I cannot change it directly). I made decend progress and now I am trying to tie it all together with MQTT, node-red and OpenHAB/HABPanel as frontend. There is, however, one problem I cannot think of a solution yet:

The audio from the interphone is recorded into a wav-file and hosted on an internal webbrowser of the esp. The filename is sequential, node-red grabs the latest URL from MQTT and stores it in an OpenHAB string item. I thought this way it must be trivial to make a webbrowser via HABPanel download/play the thing - but it seems there is actually no way to do so… Am I missing something obvious, or would I really have to write my own widget for this?

Thanks a lot!