Hi asperatology,
Thanks for reproduction steps! I was able to reproduce this in 4.7.3 with your help, and it looks like it was only Ctrl+C and Ctrl+V method of copy/paste that wasn’t working with Timelines. If you right-click and copy, then right-click and paste, it will work. I checked this bug in our main internal build, and issue has already been fixed. fix should appear in a future release, likely 4.8. In meantime, use right-click menu to copy/paste timeline nodes. Thanks!