Wait, 'before a turn'? So, every turn I can save?
Mhm. I think it's a reasonable compromise to only let you save before moving, though it is a bit unintuitive that the save button is only visible if you open the menu at the beginning of your turn instead of it simply being greyed out when it's not available. Probably a quirk of SRPG studio?
Either way, realizing that I didn't have to replay the entire mission every time I lost a critical unit was huge for me and really helped me actually learn how to play properly through experimentation, so hopefully it'll help you too.