You can’t add objects to a savf with a command but you can with a program. I don’t know how but I’m sure if you google it you will find some help.
Although it is (technically) possible to add objects to savefile, maybe half a dozen or so (outside IBM) have managed it. Review this entire thread on savefile format in the MI mailing list.
Best choice is simply to determine the desired outcome and work up an alternative technique. It will almost certainly take less time and be safer from the various recent system values.