I have been playing with tmutil snapshots here https://github.com/vimalloc/apfs-auto-snapshot. It does let you take snapshots which is great, but it also silently deletes the snapshots you have created without any input from you, which is less great. I want to setup a system where I can keep 4 quater hourly snaphsots, 24 hourly snapshosts, 7 weekly snapshots, etc (configurable of course). This setup has proven very helpful for me with btrfs in linux, and has saved me quiet a few headaches. Unfortunatally, it just doesn't work here. Something (probably time machine) keeps deleting the snapshots I have created.
I would really like to have an API where we could make and mange our own APFS snapshots, or a setting to keep explicitly created snapshots until they were explictly deleted. As it stands, I cannot get more then 4 or 5 snapshots over a one hour period without the invisible force coming in and deleting all older snapshots.
Being able to create snapshots with no guarentees that they will actually be there when you need them seems like a broken implementation, in my opinion. Hopefully Apple will fix this soon.