I have narrowed it down to the Material Properties tab -> Previews (on the right). They are rendered by the system in the background. When you make a change that impacts the appearance of the material, the system will start re-rendering the material in the background. This is used for the very small icons next to the name of the material, and the object in the Preview section.

Because the Easy Skin Shaders are procedural and quite complex, they take extra time to render. The same goes for any complex material setup.

So far I have not found a way of disabling the Preview render, but will update this question when I get some sort of solution. If anyone knows how to do this, please let me know.

Yes, but it is resource hungry, so if you have problems with Blender crashing when trying to do a final render in Eevee, try the following:

• Switch to the Fast shader
• Make sure CPU is enabled in your Blender Preferences - System settings
• If using an NVidia GPU, try switching to CUDA (instead of OPTIX)