Hi @Anonymous,
Maybe the following approach is possible? Let me know if this works for you.
1. Save the attachment to a OneDrive site via the cloud flow
2. Make sure you have the OneDrive client sync setup on the machine where you are running your desktop flow
3. Create a desktop flow with a input parameters for your OneDrive local file system folder and one for your file filter (%NewInput%) and add those to a get files in folder action

4. Add a run a desktop flow action and make sure you use the OneDrive file name
