None of their native properties have a ‘Save Game’ tag and you can’t mark them manually.
You have to either create a custom c++ child of that component or create mirror variables in your blueprint that you later apply to your component:
UInstancedStaticMeshComponent | Unreal Engine Documentation
I wouldn’t do this in blueprints tho.
I would create some custom serializable c++ component (containing SaveGame UProperties) as a wrapper/manager that can access native properties and easily save/load them and apply to the actual HISM.
For things like this it’s good to avoid blueprints and go into c++ directly.