After prompting the following, I was unable to have Firefly generate a simple flat white icon:
"In the context of data backup & restore software ui, generate a simple flat white icon with a transparent background that represents "data replication" at 2 sizes: 20x20px and 36x36px. Please reference uploaded image for style."
The resulting vector images were appropriate for something like an infographic or presentation, but not for use in a ui design.
Having a dedicated icon generation feature for UI applications would be incredibly useful.

Senior UX/Product Designer | Enterprise B2B SaaS | Design Systems & Strategy | UX Leadership & Team Growth