„It's a pretty tricky thing to get your head around – I spent an afternoon looking at diagrams and cross-sections, and talking to the engineers. But the net effect is this. Because of the different pathways through the box, and the ability of the system to use the motor and engine independently, there are in 15 different drive 'modes', or combinations of power source and ratio.
The clever bit is the control strategy, and that's what uses F1 expertise. The idea is to keep the engine operating at its most efficient revs and throttle regime. Sometimes that means primarily driving the car, sometimes it means charging the battery. This principle is the key to all hybrids but the Renault achieves it with a relatively straightforward lightweight design and no rubber-band effect when you're driving.
There's no clutch because the car is always started by the electric motor. It also uses the electric motor to go backwards, so there's no need for a reverse gear. The cars have full blended braking so often use electric regeneration rather than the wasteful discs.
The gearbox itself is a clutchless dog-type (like in F1) rather than synchro, which would normally give very harsh shifts. Cleverly though, this design uses a second smaller electric motor to control the flywheel speed and smooth out engagement. This also starts the engine.”
https://www.topgear.com/car-news/hybrid/renaults-new-hybrid-tech-uses-formula-1-expertise