I see there's a completed feature I'd like to test, labeled as belonging to 4.2.59-beta. I can't seem to download this using the launcher. Is there a way I can get it? If it works, it could save me an entire day of work.
Regarding 4.2.59-beta, constraint merging between skeletons
To access the 4.2.59-beta version, you can use the Spine launcher to select a specific version. In the launcher or editor settings, choose "Other..." at the bottom of the list of versions and type the version number you want, such as 4.2.59-beta. This should allow you to download and test the specific beta version you are interested in. If you encounter any issues, make sure you are using the latest beta version available, as updates and fixes are frequently released.
The Spinebot would normally be correct, but that version doesn't exist for download at this time.
Beta versions are only available during the beta, as release versions should be used afterward. You don't need a specific beta version to test the feature, since it's in every later version.
This feature is the duplicate button for constraints. It prompts: Hình ảnh bị xóa do không hỗ trợ HTTPS. | Vẫn hiển thị
Yes will duplicate the bones and targets and the new constraint will reference those.
No will make the new constraint reference the same bones and targets as the original constraint.
Oh. Dang. I'm trying to merge two skeletons, and when I do the constraints go away. There's about 60 of them I need to remake. Thank you regardless. 
Ah, yeah we can't yet keep constraints across skeletons. Dragging things across skeletons is the bane of my existence. 
We'll get there eventually!