Haha, my memory is blurry. I didn't realize I did joined that discuss 7 months ago. That post is not created by me and I was just sighing that the issue is 2 years old during that time. That's why I don't recall anything. Sorry to re-mention the issue.
I think I will just write a script to help me sync the keys to the other side since I just found that there are shortcut (q, e) to navigate to start/end frame. It still require one key press but is better than doing all it manually.
(Update: doesn't work. Spine.exe don't accept Ctrl key sent from external script)
Regarding the 2nd suggestion. I know the setting is for editor only . Of course this is for preview. With this change, the need to keep correcting the loop setting when switching between animations can be eliminated for preview. In fact, this change does not affect people who don't care toggling loop setting and use dopesheet to preview looped animations, as it is still 50% wrong for them anyway. However, the current implementation is causing trouble to people who do not have the habit to preview a non-looping animation with loop turned on.
I doubt it would actually be used that much/consistently to justify implementing it instead of setting looping and states directly in the runtime.
This is based on the assumption that most people would do something like "preview a non-looping animation with loop turned on"... I personally would open preview panel side by side to do preview when animating. There is no need to turn loop on for non looping animation. I guess a good design should take care of user with different habit.
If a change don't have disadvantage for both side but have advantage for one side, that change should be considered a good change, right?