You mographers probably use a simple loop expression, “loopOut()”. And I think once you’ve thought that you wanted to loop only specific keyframes like an image above. It’s easy to do with expression!
loopOut() has 2 arguments, loop type and number of keyframes. The number of keyframes is keyframe segments to loop. If you use “loopOut(“cycle”, 1)”, it loops the segment bounded by the last keyframe and second to last keyframe. See my quick expression sample GIF below. Of course, you can choose your loop type from cycle, pingpong, offset and continue.
Anyway, I recommend you to read the Adobe Help page about loopOut() expression once.
I would much appreciate it if you could give me a feedback. So please don’t hesitate to get in touch with me if you find some errors or better ways.
I hope this tips help you out even just a bit.