Situation: I get files from some clients that have no names assigned to the parts, and when i bring the model into keyshot 9 everything is simply labeled body 1 and so on.
My question is - how can i assign a material to the body in the model window vs the item tree.
Can't by drag and drop. It all works off the material name, not the part name. So, all the parts have the same material name assigned on import. You could try to mess with the import settings, which are different for different file types. Now, if that doesn't work, select all the parts in the project tree, right click and choose EXPAND. Then right click again and choose MATERIAL->UNLINK MATERIAL.
This will assign a new material to each part, so they will all have different material names and now you can drag and drop kesyhot materials onto the live view window without affecting every part's material.
You can use this trick on groups of parts as well, so you can select a number of parts that you want to all have different materials.
Fully agree with mattjgerard , but you can also drag and drop material directly on part name list in this case only the part will be affected without the necessity to unlink material.