How to get array of all materials from entire project including EngineContent folder?

Hello, I developing a simple scene, for development purposes I need to have blocks with different materials, I was thinking is instead of pre-making these temporary materials it would be better to run array quickly and apply these materials randomly to the object. How to capture all materials from the project?
Please refer to the attached image, you will see list of available materials, how to make them all to use and connect variable to it?

Sorry, the image-attaching option is no longer available on this forum.

Attach random mat to the mesh function. Get the array from the engine’s default material folder would be the best, otherwise I will have to manually make an array with 10 materials and use it with some random selection node.