I have an assembly in Keyshot but it's not finish, is it possible to add a file on the assembly in SolidWorks, and update the same assembly in keyshot without having to reapply all materials ?
Yes this is possible (I work with NX,).
When I change my files and reload it again in keyshot the material does not change.
But in NX I have choosen already a different body colour for each part. Then everything with the same colour get that material again in keyshot.
In keyshot I open first the previous file with right materials and import the new file into it and then I set only the mark ON at retain materials.
This works for me