@phila Yes, locking a layer would certainly be nice. This might happen however, only after the timeline has been re-made form scratch, the current one is a mess (according to the core devs) and adding too much stuff might be more difficult.
Duplicating layers was actually developed recently, but it is under strict review and might not come until version 0.6.6 unfortunately. For reference the current version is 0.6.4 and the next release will be 0.6.5.
For now a workaround we recommend is exporting the animation as an image sequence and then importing that into a new layer.
To save work you don’t need to export the “empty” frames that are treated as exposures.
Pencil2D has the
Export > Image Sequence > [ ] Export Keyframes Only feature, which you are to use in pair with the
Import > Image Sequence Numbered option (in the next version this is called
Image Predefined Set) where you only select a single image from the exported set, and Pencil2D will automatically select all the related images as well as palce them on the timeline according to their original frame number (as indicated by the filename enumeration).
Export Image Sequence
Import Sequence Numbered