Support for renaming a document via the workflow was added.
We added a sample workflow to describe your scenario as it has been requested a few times. This is what we ended up with:
A workflow of two states and two transitions is need. The first state renames the document based on a template that has access to the document's metadata. The renaming of the document triggers a transition to a second state. The workflow sits idle in this second state until a metadata is edited. Any metadata update triggers the workflow to transition to the first state where it is renamed again. This allows the document to be renamed upon upload and if the metadata changes later on.
Release date is uncertain as there are still 80 items in the shortlist for this version and we are still working on the SQLite to PostgreSQL database conversion command (this is one is the top priority for the next version).