I was able to customize the palette in designer. Can anyone please help doing the same with Modeler. I don't see any documentation related to palette customization for web-modeler. At least it could be better if someone guide me with the approach.
No, we don't have any docs there. The Activiti Modeler is based on the Oryx project: http://bpt.hpi.uni-potsdam.de/Oryx, and hence wasnt written by us.