Yes, a series of Kenalog injections can reduce the strip scars if they are hypertrophic or keloid. There might be a possibility that the steroid my result in loss of graphs all be it a small possibility.
Kenalog injection is a corticosteroid injection. It does not make the width of the scar smaller. It is used to flatten raised scars.
Kenalog can sometimes trigger a telogen effluvium or shedding of hairs but it is not common. The main effective is to flatten the scar.
The use f Kenelog on elevated scars can reduce the elevation. It often takes multiple injections over months separation, It should not impact the FUE grafts in the scar, but that is nevertheless a risk