I encountered this delicate green true bug on nettle. It is a capsid bug Orthotylus viridinervis  (Identification GerardL).
The bug feeds on tree sap from Elm (Ulmus sp.) and Linden (Tilia sp.) and hunts for small insects like aphids . Linden trees grow next to the garden and in the neighbourhood. Possibly the bug was looking for aphids that are always present in great numbers on the nettle plants.
References1 Nederlands Soortenregister