For getting Byproduct feature with catchweight go to Apps , install CatchWeight- Manufacturing Byproduct.
or enable configuration → settings → catchw8 → catch weight in manufacturing By-product.
Ensure that Byproduct enabled in Manufacturing settings
After successfully save settings, go to BOM (manufacturing → master data → Bill of material) while creating BOM / edit existing BOM,there is new label add Byproduct feature.
And then save BOM. when we create a manufacturing order,
After manufacturing process, by product is move to stock,