Create a category
1
Go to Catalog → Categories
Then New Category.
2
Name it, and pick a parent if it has one
Categories nest — Beverages → Energy Drinks → Single Cans.
3
Set the default margin
Either a percentage or a fixed amount added to cost.
How margin is inherited
A product with no margin of its own uses its category’s margin. If that category has none, PRODUCT_NAME walks up the tree to the nearest ancestor that does. That inheritance is what makes scanned invoices useful: when a cost changes, a price can be suggested without anyone having decided a margin for that specific product.If a suggested price never appears for some products, the usual cause is a
branch of the category tree with no margin anywhere in it. Set one at the top
of that branch and everything under it is covered.