I’m not quite familiar with the savemechanics of this game but did I googled it right, that you could only save at certain items( along the lines of a diary)?
If yes, then I would recommend just doing it like here:
Hope this answers your question, even though you asked about a month ago, but maybe someone will find it helpfull.
PS: if you got a question about it, just ask - maybe I can even give an answer ^^