Any Unknown or Unlisted Aircraft Manufacturer
Situational Awareness; Human-Machine Interface
ATC Issue All Types; Airspace Violation All Types
General None Reported / Taken
Human Factors; ATC Equipment / Nav Facility / Buildings
Working mid shift early morning with little to no traffic.  Work low altitude sectors on adjacent scope to high altitude.  Had Aircraft X on low altitude scope; changed his frequency 3 times; forgot about him.  Deviated adjacent ARTCC with no coordination and no handoff because aircraft had a 'carrot' indicating no auto-hand.  We should depict both high and low altitude sectors on one scope to create a smoother and easier scan so an event like this would not go unnoticed.
ARTCC controller reported working very light traffic on two displays during midshift. An aircraft was forgotten and violated adjacent airspace.