If you are willing to dig through xml script to save your file then you can extract/uncompress your .sifz file the same way you would a .zip file and read it with a text editor like notebook.
In the xml script, find a line that looks like this:
paste your bone guid over the guid for the faulty bone_valuenode.
This gives the valuenode a valid ID for Synfig to look up.
Repeat the above process for all errors and save the file.
Change the file extension to .sif so Synfig recognizes it.
If all missing links have been replaced then the file should open. The changed nodes may be connected to unexpected bones, but that can be fixed by changing the bone_valuenode parameter in the parameters widget for each spline vertex/origin/etc.
If you are comfortable with navigating the xml script and you remember the name of the bone that the node should be connected to then you can scroll down to find the proper bone instance (i.e. “Bone 20”) and copy the hash for that instead. This is not strictly necessary for recovering the file though.
I got it working, but the result is a little messy…
Your file had bone_links, but no skeleton layer, so I pasted some bone script in. That was the only thing I changed besides the guid hashes. Your guy exploded into chunks on my end, but I didn’t have girl character 1.sifz so maybe it’ll be fine.
I just delete the skeleton layer before close the file and also save it. Didnt nothing else ( copy paste) @rodolforg after i cant open that file again.
Girl character file is another sif file and i copied some parts from that for boy char.
I will never use skeleton layer again😁. Even rotate layer also work well than skeleton layer.