Damn, I was hoping we'd have some luck.
I would never suggest to a Linux person to switch to Windows! :nerd: I use Lubuntu in VirtualBox for most Linux testing. Even in a VM I'm not seeing lag when dragging a new bone with the Create tool. If it's something GPU or otherwise hardware specific, changing distros may not help.
It's hard to tell from your video, if you move the mouse and then stop and don't move it at all, does the new bone catch up, or does it freeze some distance away? If it freezes some distance away, it could be that Spine isn't getting all the mouse events for some reason.
Tracing through everything that happens with the Create tool, we found some work that could be avoided and made some changes for 3.8.07-beta.
Can you try this: enable bone compensation by clicking Bones in the Compensate group on the main toolbar, then try the Create tool. If that improves things then likely it is fixed in 3.8.07-beta.
