Update attached file using contents of another field

Hi there! I'm troubleshooting a workflow we once followed but has since been deprecated.

In our filing of documents, we want to rename attached PDF files (in a field named Attachments) that come in as 'unnamed attachment' with the contents of another field (named ID) when a box in a field named "Update Attachment" is checked.

This was previously set up using an Automation in the base, with the trigger being "When a record is updated.." and the action being "Run a script" As it turns out, the JS that ran is no longer valid, so nothing happens when the box is checked. To make matters worse, the script was inadvertently deleted during troubleshooting, so we no longer have a reference 😞

I have found posts where folks are asking for something similar, but they're old enough that the methods no longer appear to be valid. The problem seems small, but the solution appears to be complicated.... If anyone has any insight, I'd really appreciate the help. I'd also be happy to provide any additional functional examples for context.

Thanks so much!