I tested again with new projects, knowing that extra info about curves and I still can't properly work. The thing is, as long as you add an animation with keys to certain body parts, if you want to add something afterwards (like vfx particles for example), you just cant. It ll mess the existing animation so the only way is to be proactive and keep things invisible and when needed make them visible. For example, think of this: You have a mole that goes into his hole and leaves dust clouds behind. You make the mole go down, you make the dust cloud, replace sprites to make it look like it dissolves, then you realise you want two extra mini clouds on the sides to go left and right. That's where the issues start. I add the extra sprites at the key I want, then in all other frames they disappear. I understand though that this is core functionality. Then, I copy the frame which i created the mini cloud, and paste on an empty keyframe. That will freeze the rest of the animation which is something that doesnt make sense. I am coming from a flash animation BG and I ve used keyframes and modular animations and the way I am used to things working makes it really difficult to do even the simplest of animations here,even though its an amazing software that has a lot of potential. This is probably another topic, but when adding a new sprite in the scene, all frames from the one that the sprite was added and onwards should contain the sprite. Also, only the data inside the key should be copied when copying the keyframe, not everything. If I wanted everything, I would have "key all" first. Also, the timeline copy/paste functions should not be affected to whether I have selected something in the viewport, that also doesnt make sense (even though it can be a nice feature), because with complex animations, you may need to keep a sprite selected (because its hard to select with everything that is going on), while copying/pasting keys around. Imo, the timeline needs to be tweaked to be independent (selection-wise) from the viewport and you can add/remove stuff without affecting the rest (even at bone hierarchy level). Also some clear indications of whether something exists in the timeline would be great (or the ability to set which properties you want to see displayed in the timeline, like width, opacity, etc.) Check FL Studio's automation for more insight on this. Since I mentioned everything I want from Spriter, I might as well mention this too: if Spriter implements Grouped animations (think sprites in flash animations) and masks, I ll happily buy it for my team.