ComfyUI
The most powerful and modular stable diffusion GUI and backend.
ComfyUI Screenshot

This ui will let you design and execute advanced stable diffusion pipelines using a graph/nodes/flowchart based interface. For some workflow examples and see what ComfyUI can do you can check out:

ComfyUI Examples https://comfyanonymous.github.io/ComfyUI_examples/
Installing ComfyUI https://github.com/comfyanonymous/ComfyUI#installing