I would put in:
EN-EN (Airwork).
Other examples:
ML-AY(25VOR/DME)-ML(16ILS) for instrument approach recency
BK-BK (3 CCTS) for night recency for example.
I use to annotate if the flight was under I.F.R. procedures too, as some airlines want to know how many hours multi-engine under I.F.R. you have as well as the number of instrument flight hours.