Is there a simple way to properly rotate a Smart Material? This was asked (here) before, but the suggested solution using a filter is not working at all for the "Wood Ship Hull Nordic" smart material (maybe it works on a simple quad, but not a model with multiple UV islands).
Having to orient all UV islands to match a specific orientation (such as for wood grain) can be a nightmare, especially since there is no standard for this. It also limits how well we can pack UV islands. Some wood smart materials are oriented with grain running vertical while others run horizontal is seems. Trying to find all the places that need rotating inside a smart material is a also nightmare and that requires us to make rotated "duplicates."
It seems like we may just be force to just make our own substances in Designer where we can expose a single rotation value.
No simple way unfortunately, and you are right in that using a transform filter does not work with islands, it just rotates the smart material off the islands. I normally just unwrap with this in mind, ensuring that unwrapped islands align with each other in the direction of the material to be used. If they are all 90 degrees out, it is often quicker to rotate all in the modelling software and re-export then update the project configuration in Painter than it is to find all the necessary rotations in a smart material.