Key frames disappear sometimes This is bad! Fixed!
Buttons on top of timeline disappear some times I think this is something going wrong with laying out the UI. I haven't been able to reproduce it. For now, most likely you can fix it by resizing the Spine window.
In the list to the right, to select several things, you have to hold down ctrl (on mac) Should be cmd on Mac, fixed!
overview keys affects all keyframes in the column This should only affect the visible keys. I'll look into it.
Lock animations & bone colors Maybe at some point.
marker for last frame in animation Nice idea, done!