Overview
Advanced ComfyUI workflows are extensions of the same pipeline. Image-to-image replaces the empty latent input with a VAE-encoded image. ControlNet modifies the positive conditioning before it reaches the KSampler. InstantID also adds model and conditioning logic before sampling. Ultimate SD Upscale replaces the ordinary sampling stage with a tiled image-to-image process.
Without a clear model of the baseline graph, advanced workflows appear to be arbitrary wiring. With the baseline understood, each extension can be identified by the stage it modifies.