Fascinating footwell video of a V8 Supercar lap. The car has an ignition cutout on the upshift so the foot stays flat on the accelerator during the gear change. The heel and toe (clutch in and engine blip) is something you will not see in pretty much any racing series now, but they wanted it to stay in Supercars.
Since around 2007 they pioneered 'seamless shifting' in F1, wherein - using some very trick arithmetic - two gears momentarily engage at the same time, so the next gear is 'queued' in milliseconds and the driveline simply keeps going with no interruption.
Here's Fernando Alonso having a go in a Supercar in 2022 at Albert Park, like he's never known anything else. I don't think he even blinks.
https://youtu.be/1f5QlfrODu8