Use the Material Editor to create materials and convert them from one file type to another.
If you need a material for OpenGL, see the section to follow.
Click Create/Convert > Create Material.

Select the material type you want. This create that material.
Another way to create a material is to right-click in the Material Tree View, click Create Material, and select a material from the list.

Create a material that will work in OpenGL.
Interact with the Material Editor to select one or more materials from the Material Editor list, then make that selection available for other operations in Python.
Use getSelectedMaterials() to return a list of vrMaterialPtr (material pointers).
Convert one kind of material to another.
In the Menu Bar, select Visualization > Interactive Material Preview. When enabled, dragging a material (without dropping it) over an object provides a preview of how the object would look with the material applied.
Ensure Interactive Material Preview is enabled.
Do one of the following:
Use the material parameters to make changes to a material.
Select a material from the Material Preview Pane.

In the pane to the right, use the parameters to make changes to the material color, texture, incandescence, transparency, displacement, raytracing, and more.