Hm, now I am even more confused 
Which part of the process exists? You just described that I need to go through those 5 steps and I am unsure about step 3, how is that suppose to look like?
I understand that arrays of structs might be actually better. I could define an interface with Save/Load functions that would handle making/breaking that struct for that particular actor. However then I need to keep separate array for each type of actor, right? Or keep single array but each struct would need to also hold class of Actor from which it would spawn. However that’s that great way to have a huge save files as those classes are stored there as a string…
How does it actually work when you have a save file with some structure and you change eg. delete some variable from the struct and try to load that save? Is there some safety mechanism or it will simply fail and that save file is impossible to recover? I remember from my young days working with binary save systems and that for every change to structure I had to version it and then do conditions so it can read/write those bytes in a correct sequence.