The simple answer is that there is no real protocol among EV drivers, unfortunately.
In the early days, when there were far few early adopters there was a more accommodating comradery, and although fewer public chargers, there was more of a "after you," "no after you" culture. However, there are far more EVs on the roads, and for many filling with electric juice is just another type of fuel and the drivers expect to just turn up to a forecourt and quickly fill up rather than embrace the EV Culture. So now the culture is just every man/women for themselves.
Just don't get me started on the whole issue of whether you can unplug a car that has finished its Rapid charge! Can you, Can't you unplug and take over the Rapid charger? According to the people I spoke to at Grid Serve, they say the Charger belongs to the Charging provider and so if the charge has finished, then you the next EV driver can remove the charging cable if there is a bay you can use. However, many drivers say you shouldn't interfere with their car. In reality, if the session has ended the plug should be unlatched, so you've no need to touch the other car just remove the Rapid charging plug and cable belonging to the Rapid charger. I'd suggest if you do this you take photos on your phone as evidence before doing anyTh