Hi, thanks for the welcome!
I probably should’ve clarified more, but I don’t make sprites in Synfig. I instead use sprites to make animations in Synfig. Here’s a screenshot of my project:
Quick disclaimer, I didn’t make the sprites seen in that image. What I did do was put them together with some .lst files, then set them to constantly loop, effectively making a looping background seen in fighting games like Street Fighter. Of course, there’s more to my project than just that.
Speaking of workflow, the “set-up” phase is a bit of a pain, but the payoff is worth it if you intend to reuse the character later. I first extract the sprites from the sprite sheet using this handy program called Alferd’s Spritesheet Unpacker. Then, I take the images of certain groups of sprites (such as a running animation) and check the dimensions until I find the largest dimensions of the group. Then, I use paint.NET to create a canvas that has dimensions 2 pixels larger than the largest dimensions of the images (this is because Synfig seems to distort the pixels on the edge of an image… or at least it did in 1.0.2. I’m not sure if it still does this in 1.2.0). After that, I drag the group of images into paint.NET and import them all onto the canvas as layers. I make sure each image is positioned properly so the animation will look right, and after that is done, I copy each layer and use Ctrl+Alt+V to paste them into new images. I save each image as 0.png, 1.png and so on in the same folder. Finally, I create a .lst file (or a few depending on the sprites) so I can use that animation in Synfig.
As you can tell, the set-up phase is a bit tedious and time consuming, but I’ve optimized it as much as I can. The payoff of this process is that you don’t have to redo all that work to set up a character, especially if you set them up in a .sifz or .sfg file for later use (even though I’ve had some mishaps storing their Synfig setup in .sifz and .sfg files…).