It's a rather out-there (non-serious) idea where all the usual 'stuff' of a GUI is actually made out of dynamically-simulated-CA/RD cells interacting with each other.
Let's say for example once one had developed some way to reliably simulate a dynamic but smooth and stable enclosed area with a boundary (like a bag?), well you could call that layer a 'window'-ish-type-thing and constrain the sub-simulations (ie the window-widgets) to only grow inside the window. Window-docking could perhaps have behavior a bit like bubbles-adhering-to-each-other as a natural outcome of the simulated-nature of them and wobbly-windows could be made to be a natural outcome of there being the wave-equation as one of the formulae being used, and other things like that.
It's definitely an out-there idea not really intended for regular-consumption but I think it could be super fun to explore especially for playful in-game-UI use-cases.
Edit : Ahah I just noticed the "other commenter" is you