Method of defining material to blocks

is there a way to define material in to blocks. Or I need to rerun everything and not to use blocks anymore for material definition purposes

I’m not sure I understand your question. Blocks can have specific materials when defined or acquire any material as instances once they are inserted if you assign a “by parent” material when you create the block.
You can then have various instances of the same block with different materials.
You can assign the material directly to the block or by layer.

Yes. I think that is my problem. I defined many blocks to easy the workflow. But I did not assign any material at the beginning. Thinking that I can assign later. Now my blocks don’t accept material definitions. I need to study “instances” and “parent” more closely. But on the other hand I need to do all blocks again. Bump…