To validate that I understand what you're asking for:
the input file,, as an example, would be something like this:
12345-27-Report.pdf
Your preprocessing script would parse the name as: <OrderID>-<Qty>-FileName.pdf
The input file is always Read from the hotfolder then removed. It's move to a temporary location for processing. The removal is so that Core doesn't try to process the file again.
I believe you'd need to have 2 workflows and 2 hotfolders.
The Hotfolder #1 would have a preprocessing script (note could also be an external script). Workflow #1 doesn't need to do anything much, could be a join or save, really doesn't matter. All the work is done in Workflow #2.
HF #1 Script would:
1. Save out a copy of the input file (12345-27-Report.pdf) to a known directory.
2. Write a csv file into HF #2 with the files 12345, 27, 12345-27-Report.pdf.
3. This will trigger Core to read the CSV file and send to Workflow #2.
