I created a Board Support Package (BSP) for the Makerfabs 3.5" touch model.
I posted on the details on the forum as well Introducing the Makerfabs 3.5" Touch TFT Display BSP for Squareline Studio! 
- My projects - Forum - SquareLine Studio.
Not sure if this helps or not. I hope there is some similarity between them as they all come from Makerfabs.