I spent some time configuring a setup similar to this. Unfortunately, there's no simple way to do this. There's only {{job.trigger.file_arrival.location}} parameter, but that is pretty much useless, since it points to the directory that we are watching instead of the file that arrived.

For your situation, I'd use dbutils.fs.ls(dir) and filter based on your needs. Then feed the path of a single file to spark or something.