AICUS
When first invented, it was called AICUS: "Acting in command under supervision". It was something that a co-pilot did in special circumstances. It was supervised by a pilot in command trained in the supervisory role and appointed by the operator for that purpose.
When first invented, it applied only to multi-crew aircraft and some single pilot aircraft that required the gaining of experience under a mentorship scheme that went beyond simple dual instruction. It formalise the roles of copilots undergoing command training in the left hand seat (aeroplanes - the reverse for helicopters) and the Training Captain supervising from the right hand seat.
It could never be logged by a co-pilot operating in his/her normal right seat.
It then was totally destroyed as a scheme by CASA to the current point where it is just co-pilot time doing co-pilot things...
Stay Alive,