I'm posting this to see if anyone else with a Huntsman V3 Pro Mini is experiencing the same issue.
My Huntsman V3 Pro Mini is detected correctly by Synapse and Chroma Studio. The keyboard functions normally, and Quick Effects work without any issues.
However, when I switch to Advanced Effects / Chroma Studio, I am unable to edit per-key RGB lighting. The color selection controls are greyed out and display the prohibited symbol (circle with a slash). As a result, I cannot assign custom colors to individual keys.