Making GIFs with GifGunGifGun action sends rendered files to GifGun for gif creation.
It works only if you have GifGun installed on your machine.
Adjust its settings either by opening GifGun itself, or using the action button
Note that rendering GIF out of a long and large composition might take significant amount of time. This part of render can't profit from the BG Rednerer Max's multiprocessing feature.