Use designated parking space as a garden

I would put a small fence between the two parking spaces and then a sliding gate between the fence and parking space 2. Or alternatively, the sliding gate can be big enough to cover both parking spaces.
At some point, you will have to take a trailer into the garden and then you'll be glad to have the lowered curb edge.

It was done like that at my mother-in-law’s. The two parking spaces for the still unused granny flat are marked next to the terrace - but just grass. The fence simply has a double-winged gate.