Hi everyone and @EricL
With a new children to our family, we have subdivided a new bedroom and we are in the process of painting the plastered wall, but during that we find the light switch & socket should better to move to the wall closer to the door.

We haven't done this before.. how should we instruct an electrician to do to reduce our work in restoring the wall he will cut in?
1) When the electrician is cutting a new rectangular hole on the dry wall to put in a new light switch, we should ask him try to keep the "small rectangular drywall part" for us?
This way we can tuck "that scrap part" into the old hole without worrying to find extra material, minimisizing our effort to plaster repair the wall?
2) After we fill the hole with the rectangular part ,
What material and tool should we purchase to adhere that to the wall? Plaster?
Which brand to use for a small job like this?
Thank you for any advice...!