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With the upcoming SNAC/SNAX implementations from MisterAddOns and UltimateMister whats the best way to manage MemoryPak Saves?
The Everdrive64 could backup saves to the SD card - and I do have a Sanni Cart Reader that can back up the Memory Pak.
I remember on the N64 you could hold START when booting in to some games with a Controller Pak inserted and pull up a management menu; Mario Kart 64 was one of them. I've not tested this on the MiSTer core yet so I'm not sure if it works/is practical.
As for PC tools there are quite a few around:
https://bryc.github.io/mpkedit/
https://savefileconverter.com/