Sorry I meant long term history, IE alternative uses many years ago
The layout at the West end of the station was altered in the 90s in preparation for the Channel Tunnel services. Before that Platforms 3 and 4 were accessible from the original route via Redhill as well as from the Sevenoaks direction.
The station was considerably rebuilt by the SR in the 1930s and from then on P4 (but not 3) was signalled for passenger departures to both routes, which made it more useful, though I don't ever recall it being heavily used. I would imagine it was an ideal place to place parcels vans for unloading/loading.
Without access to the station workings, I can't be more specific, but in the electric/diesel era as well as the Redhill trains there was a school train from/to the Sevenoaks route which probably used it, and in steam days there were random Sevenoaks-Tonbridge trains that could have used it as well as Redhill trains.
There's lots of info here:
https://kentrail.org.uk/tonbridge 3.htm