How to determine the physical location on a RS-485 daisy chain / bus topology?
It is a bus structure. By definition is does not matter where each device is physically placed.

If you need geographical addressing you could try this approach:


Connect the master node at one of the ends of the bus
Each node must have an extra wire (ie. one input and one output wire) that goes to its neighboring nodes (a simple GPIO will do).
When that wire has a specific (default) state - the node stays silent and ignores all traffic.
At power-on each node does not have an address. The master pulls the extra wire low (or high) enabling the first node on the bus. Sends a "set address" command on the bus (that does not have a destination address) - of course only the first node acts upon this message.
The master sends a "enable control line" to node 1 (that now has an address), this makes node 2 listen to the bus.
The master sends again a "set address" command (that is ignored by node 1 - because it has an address already) that sets the address of device 2.
Rinse and repeat for all nodes.