As standard, the 4 Series' rear seats split-fold 60/40. Once folded down, the rear seatbacks sit at a slight angle rather than fully flat, and the parcel shelf is fixed, so there's a restriction on the height of objects you can carry.
However, you can spend a bit extra for seats that fold 40/20/40, with a useful ski hatch through the middle for longer items.
The front seats automatically return to their original position, so the driver won’t need to reset them every time someone climbs into or out of the back. The seats themselves are easy enough to fold forwards but can get caught on the rear seatbelts.
The 4 Series comes with a seatbelt-extender, so you don’t need to reach back over your shoulder to buckle up when setting off. However, it’s odd that lumbar support for either front seat is not standard on any model.