load data from parquet and display metadata in ner.manual UI

dear explosion team,

I have a parquet file with a couple of columns which I want to use as input for ther ner.manual recipe. I managed to get it to work with a little trial and error (the parquet loader isn't documented at all). I want to show the filename (which is a column in the parquet file) during annotation, to make it easier to go back to the original source of a text, in case parsing or ocr issues get surfaced during annotation. But I don't even know how to start implementing this trivial change.

Do I need to create a customized version of ner.manual or is there an easier way to modify the interface? The loader seems to stream in my metadata correctly, I can see the "filename" variable, when I run window.prodigy() in the javascript console.