How does a custom node in a material output a texture?

You can sampling it in custom node.

Thank you for your questions and answers. Could you please provide sample screenshots for reference?

What do you need to do with the output? Given this example screenshot you could connect the Float3 output (expect it is RGB) of the custom node directly into the BaseColor pin and skip the texture node

Roy is right, if you really want to sampling texture in a custom node, just

SamplerState Sampler;
return Texture2DSample(Texture, Sampler, UV);

What type of value does the return value of the cmot material attributes type correspond to in Shader?

2AD6FB3A-C4DF-4178-86F8-8199B09858E3

I suppose this is a collection of material properties, but I never used it. You don’t need additional outputs when you return “o” on both