For the control of lamps, shutters and sockets is a variety of switches KNX available. Unfortunately, these are outrageously expensive and due to the required amount, they are are the reason for a huge part of the hardware costs.
If you instead relies on a combination of KNX universal interface and conventional buttons, you save a lot of money and and it looks very subtly.
In all places where I do not need more than 4 buttons, I could rely on the above-named combination. Only in 2 places I had to use 8x KNX push buttons to avoid my wall to be covered with unnecessarily many switch boxes.