User should be able to split timeline to slides. As reference I would use cut tools from a video editing or digital audio workstation software, where you set the start and end position of the clip.

This comes handy when you import animation from external tools, and want to create states from that, since the current workflow for doing that includes lots of duplicating slides and deleting and moving keyframes.

What this tool should do is:
1.Cut the desired part of the timeline
2.Create new slide
3.Paste the cut part of the timeline to the new created slide

See original suggestion QT3DS-783 for one UI proposal.