From what I understand, you have completed the Augmented Reality Training and achieved the grapple boost.
To chain the gliding, first you need to grapple at a long distance. Then when the Batman is grappling, in the mid-air, double-tap "space" and grappling speed will increase with a slight change in sound. Batman will move faster towards the grappled target and instead of landing at the target area, it will launch high in the air and then you can hold "space" to glide.
Again in mid-air you can grapple at some distant target and proceed as mentioned above to chain glide.