When relaunching a kite with board still on my feet, the lines rub on the the toeside leading edge of the board when the kite is still on the water before relaunch. Not going to be good doing this on lines too often.

Is there any other technique to avoid wear and tear on lines?

Keep the kite flying at al times

Have the board on your feet behind you , ie like the body drag stance

bend your knees and try to sink the board a little with your body weight.
You don't need to be at full stretch.