Changing materials sample cube in SU 2025 Mac

How to change materials sample cube to rectangular flat image in SU 2025? I saw it somewhere, but can’t find anymore. Does somebody know?

At the moment there isn’t a way to make an advanced material show anything but that cube. There are plans to add other preview shape options.

For any non-advanced materials, those should show up as the normal flat image. If you are working on a model that might need a mixture of old flat materials and new PBR materials, you could go into Settings, Graphics, and uncheck the options to automatically enhance materials. Then those ones will keep the old rectangle thumbnail.