That wasn't my experience. At least for one item. I had the Weapons crate in my inventory. Opened the save in the editor and the slot where the crate was showed as "empty". I was afraid to save and end up deleting my weapons crate.Unless there's suddenly been a massive overhaul, or a ton of new items that were added, an update shouldn't affect the save editor. Even when new things have been added, you can still use the editor if you already have said items in your inventory as well. My own experience back when things like gaia leaves got added, couldn't add it into inv via the editor but once I got 1 I could change how many I had.
It's been updated though.