Baking normal maps from compound high-poly models I learned how to bake normal maps and it's working well so far. My model is a simple oven to which I'd like to add some rivets. The model will be used in a game, so the rivets should only exist in the normal map. 

I know how to do that by adding geometry to the high poly model, but if I later add some more parts to the low poly model, I think I have to redo the work of adding the rivets, or I have to also add the parts of the low poly model to the high poly one. I'd like to avoid this work and add geometry in a non-destructive way.

My question is: Can I add geometry to the high poly model as objects so I can move them, use the array modifier etc?

I tried to parent the rivets to the high poly model, but they are ignored in the baking process.
You can bake several objects into your lowpoly.

Simply select all of them, then maintain Shift and select your lowpoly. Make sure the lowpoly is outlined in yellow (meaning it is Active) while other objects are outlined in orange (meaning they're Selected).

In the baking options, check "Selected to active", and hit the "Bake" button.

While many objects can be selected at the same time, only one can be active. It's usually the last selected object, and its name appears top left of the viewport.