JabRef 5.3 Custom Export Filter and .layout file

I have a custom export filter used fro converting .bib files into .html files.
In the main .layout file, I have a couple of conditional outputs managing different fields. For the fields, pdf, code, and slide, I have a conditional output as below

\begin{pdf}<a href="\format[FileLink(pdf)]{\file}">[pdf]</a>\end{pdf}

In JabRef 4.3, using this filter, I managed to generate links to the papers’ pdf files. Since upgrading to JabRef 5.3, this conditional has not worked as expected.

Any advice is very much appreciated.