ᐅ Installing cables afterwards in prestressed hollow-core concrete slabs

I’m currently facing a (DIY) building challenge ;-)

There is an outbuilding with precast prestressed concrete slabs as the ceiling. These have a V-joint, similar to what you might know from precast element ceilings in single-family homes. A cable for a ceiling light needs to be placed in this joint, which will be plastered over afterward.

Now, gravity is quite a nuisance, and I’m completely stuck: How do you secure the cable “up there” so it can be plastered in? Something sticky to temporarily hold the cable?
Hammering cable clips into concrete?
Plastering over directly and pressing the cable into the fresh plaster?

It’s a rigid cable, about 5m (16 feet) long.
Does anyone have a practical tip?

I would start by trying a construction adhesive. Clean the concrete beforehand.