someone in the technical area commits an offence but the offender cannot be identified?
The head coach is shown a red or yellow card (depending on the offence).
a team official leaves the technical area to watch from the stand and then returns to the technical area?
This is allowed.
a team official uses a laptop or other electronic equipment in the technical area?
This is allowed, as long as it does not cause arguing, dissent, protests, etc.
someone is a player/coach and wants to be a substitute for the game?
They must be shown on the team list as a substitute and not as a team official. They are allowed to act as a coach until they go onto the pitch to play.