Component materials

i was wondering if there is any way of importing more materials in to visual components. the selection is quite limited and i was not able to find any add-ons or anything online. thanks

you can define your own materials like explained in the Help file : Adding New Materials

In Documents - Visual Components - 4.X - My Materials, you can also add your own materials to be displayed in the list of materials

what file type is used for these materials?

Alternately, you can add manually the materials by modifying the Materials.xml file located under
C:\Users{your user}\Documents\Visual Components\4.8\My Materials
I recommend you first adding an user material from the UI before modifying this file so you understand the properties each material needs.