Checkpoint64 has a preset for Cemu (Wii U): it already knows where the save folder is, backs it up automatically and keeps every version. Everything this site has on Cemu (Wii U):
Cemu (Wii U)
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Save file location
Windows:
%APPDATA%\Cemu\mlc01\usr\save
macOS:~/Library/Application Support/Cemu/mlc01/usr/save
Linux:~/.local/share/Cemu/mlc01/usr/save -
Backup guide
Emulator save states are easy to overwrite and rarely backed up. Checkpoint64 gives them a full version history and cross-machine sync — RetroArch, Dolphin, PCSX2, DuckStation, PPSSPP, RPCS3, and Cemu all have presets. Free download.