Save as
From Synfig Studio :: Documentation
Saves the current project under a different name.
Use an extension of '.sifz' to save a compressed file (as of synfig 0.61.07). If you use .sif then the files tend to get pretty large. The best thing to do is not to use any '.' in the path at all, and then synfig will append .sifz (if it's new enough) or .sif (otherwise).
