Hey akura_, the layer system isn’t complicated but like Richard said, it’s buggy. You can option/drag frames in a layer to duplicate them, but not copy and paste (try it and Poser will probably crash). Using layers slows down Poser considerably on my computer, so I only use them to accomplish a task then collapse layers when I’m happy with the result. For instance, I might make a character breath in the base layer (keyframe a single breathe then copy and paste every 100 to 200 frames) and then create a separate layer (set to add mode) and add a few spline keyframes to modulate the base layer, making each breath a different intensity.