Create a sign and type the following: {c:SAVEID|} This will create a blank sign. Switch to another element and click it. It should link you to another save. From there you can fav the save.
Using search (similar to searching by user) you can use "id:SAVEID" as the query, there's also a console command to do it, but I have forgotten (something like !open or !load and then the save id)