Looping / Alternating builds or slides?

Hi Keynoters.

wondering if there is any way to have something loop on a keynote slide? Specifically I want a pair of images to alternate until I click.

Yes, I could make a movie for each of these occurrences that loops, but would rather know if there is any kind of looping function hidden somewhere that is not obvious, or a set of steps that creates a loop. Actions, build in/outs, transitions, I'm open to anything.

This was asked a dozen years ago and it was impossible then, but maybe it is now? seems this would be a useful and not to difficult feature to incorporate into the Build Order menu (like a basic "Go To" command?)

thanks for any help.