When i was there last week i asked one of the Smiler crew and they said there's no single rider queue at the moment - but i could ride if i joined the main queue.Unless I'm missing something... single riders isn't possible due to social distancing? You can't be put with anybody outside your household.
I didn't because there was a huge queue and i was with someone who didn't want to ride.
As far as i know it's one social bubble per row, so single riders get a row to themself, on thier own.