For the avoidance of doubt, and to fill in one gap in my understanding, there is only one Kit buffer per (closed)project - I recall a discussion years ago where there was a suggestion there were more, and there’s an element of truth in this too
Whilst working within one solitary project a number of Kits can have their own working buffer states, so a few patterns using unique unsaved Kits will sound as they did when you hop back and forth, but, crucially, when you exit a project, the last Kit buffer is the only one retained (this is why I speculated that there was only one (scratch) Kit in play over the preceding years in the case above)
If you return to a Project with one unsaved Kit the scratch Kit will indeed be used, but that’s a bi-product of a larger design choice, quite why there’s any temp Kit buffers held within an unopened project is a mystery to me (the reason it’s not then all Kits’ buffers is likely down to space, only the active Kit can have multiple temp Kit buffers. So someone exiting a project with more than just the last kit edit changed will be finding that all preceding edited Kits (to the last) will be returned to the last saved state or the default if not saved at all
Some of the background to this can be seen in this old AR chat, but the Kit paradigm is exactly the same for A4
Here’s it’s suggested only two temp kits in an active project, but I just tried and it worked with three (at least)
It’s well known from a number of threads, but I am not sure how explicit teh manuals are on pre-saving Kits before saving a Project, but I believe the workflow is the right one, Kits should be explicitly saved, not assumed so because every tweaks you made whilst playing would wreck a kit