Hey Daphnis26 (and everyone) -
After some research and discussions here, it turns out that the wind directional source is set up in code to allow change to the values only through its UProperty directly from Slate (so from the details panel) and not through blueprint. Our Engineers are working on changing this function and opening it up to the editing in Blueprints. I unfortunately do not have a timeline for this change, but it is now fully on our radar.
Thank you all for your patience -
Eric Ketchum