D&D General What if we gave dragonborn four arms?

[Corinnguard]

but in what way?

Good question. Back in 3e, you could have it where magic was used to 'sculpt' unborn dragons while they were still in the egg into a number of draconic forms. There were several examples of this in 3e- Draconians, Noble Draconians, and Tiamatspawn.