Your presumption that there’s an “edge” is at fault here. Consider the surface of the ballon (or rather- a bubble) - it’s continuous, just like our universe. And that’s why it’s hard to explain how a 3D space can expand seemingly without a center point - because said center point is not within the constraints of this 3 dimensional space, just like how the center of a balloon or bubble is not on the two dimensional surface but in the center.
so just like the surface of an expanding bubble, the expansion of our universe doesn’t happen in a plane we can conceptualise easily - it’s a 4 (or possibly more!) dimensional expansion, of which we are just the surface, therefore the expansion appears as if everything literally drifted away from everything - which should be impossible in a 3D space but not when you add a fourth axis.
Your presumption that there’s an “edge” is at fault here. Consider the surface of the ballon (or rather- a bubble) - it’s continuous, just like our universe. And that’s why it’s hard to explain how a 3D space can expand seemingly without a center point - because said center point is not within the constraints of this 3 dimensional space, just like how the center of a balloon or bubble is not on the two dimensional surface but in the center.
so just like the surface of an expanding bubble, the expansion of our universe doesn’t happen in a plane we can conceptualise easily - it’s a 4 (or possibly more!) dimensional expansion, of which we are just the surface, therefore the expansion appears as if everything literally drifted away from everything - which should be impossible in a 3D space but not when you add a fourth axis.