You can't at the moment. You could add this behaviour quite easily though. Let me know if you'd like to attempt this and I can explain in a bit more detail.
So I could add this feature to the animation editor? Wow, that would be pretty cool.
Even if it is basic tools to offset sprites, it can make the animation editor that much more awesome. Are you planning to add this feature in future patches of 2dtk ? It would make for a solid animation tool as well.
With that thought in mind, I made a mockup with suggestions that might bring the animation editor even cooler. These pop-ed into my mind as I worked more in depth with the editor on my game. (I've worked as a sprite editor in the industry in the past, most of these suggestions come from my experience with those engines I worked on.) Just to show what might be useful for animators out there and speed up the workflow process. (And if ever you plan to update it with more options that will benefit other devs.) I know it is a lot of work to implement, so not expecting nothing out of this. Just food for thought.
(Sorry for the long post, I guess this could be posted in a "could be cool to have feature post".)
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Quick Explanation ] :
The Flip Horizontal and Flip Vertical Main Button - When you click it toggles ON/OFF the horizontal/vertical flip option for all frames
Mighty useful if you have a big Walkcycle. Make all the frame look at the left. Creating the right facing direction can be done simply with one click! Wow. This is quicker, and clean. You save space and it is really less tedious then manually flipping horizontally the frames, say in Photoshop. Great for being efficient.Hide/Unhide toggle options for each frame - When the toggle is set to ON, the sprite will be hidden when the animation clip plays
The Hide/Unhide option is a really powerful tool to quickly see if your animation could be done in less frame and still feel right. Making it easy to see if the frame is valuable or not. When the hide toggle is on, the animation simply skips this frame like it's not part of the anim clip.Delete frame - When you click the - button, the frames get deleted
After you hidden the frame, you realise that frame doesn't look good. You want it out. Instead of deleting all the other frames, then adding the autofill again, you simply delete this frame. Takes one second and it's done. Nice and quick.Horizontal and Flip toggle options for each frame - When the toggle is set to ON, the sprite will flip horizontally and/or vertically
Basic but mighty useful when animation sprites. A lot can be done with this feature. Save space, you don't need to manually flip the frames in Photoshop, nor do you need to code anything.Offset X/Y Area - Offset the Sprite in the X and/or Y value when the animation plays
Another basic nice animation tool. Instead of making the sprites bigger with empty space, you can simply offset the sprites directly in the editor. Quickly making it easy to tweak and see live if the animation looks good.