You posted a screenshot of a screenshot that has a video. It's not clear what the problem is? If there's another discussion that has a video of the same problem, please link to the discussion.

If I open the spineboy example project, select the head mesh, select vertices, then switch between Animate and Setup modes, the selection is kept. How can I see the problem using the spineboy example project?

yugutou Just to be sure, I tried it too, but I couldn't confirm the bug that the selection in the animate mode is lost when switching to the setup mode in 4.2.28. I tried both the mesh and the bone. Here is a video of the results I tried:

So please tell us the exact steps that will allow us to reproduce the problem.

yugutou Oh, I see. If you encounter the problem again, please let us know.

yugutou Thank you for reporting the issue with the video! Now I understand the problem, so I have created an issue ticket here to fix it: EsotericSoftware/spine-editor804
We apologize for the inconvenience, but please wait until we have fixed it.