Definitive Edition and the older Classic directory are separate. Keep each save folder intact inside the correct PlayerProfiles tree and do not flatten .lsv files between editions.
For this PC reference, the documented storage is Windows: %USERPROFILE%DocumentsLarian StudiosDivinity Original Sin 2 Definitive EditionPlayerProfiles<profile>SavegamesStory. The known file or folder pattern is one folder per save containing .lsv and companion preview/meta files. Definitive Edition organizes saves by Larian player profile and per-save folders. The per-save directory, not just the .lsv payload, is the practical unit for backup.
Backup guidance: Close Divinity: Original Sin II – Definitive Edition, let the launcher finish any synchronization, then copy the complete documented save directory to a dated folder outside the live path. Preserve companion files rather than selecting only the newest-looking record. Steam/GOG cloud features can synchronize the player profile. Preserve an offline PlayerProfiles backup before resolving conflicts. Launcher and cloud context matters because The active Steam, GOG installation determines which local profile and cloud copy can overwrite the save. Identify the storefront and account before restoring files.
Compatibility and recovery should stay conservative. Treat saves as version-, storefront-, account-, and mod-sensitive unless the game or a separately verified migration workflow proves otherwise. A similar filename or extension is not evidence that two releases are interchangeable. If the expected progress is not visible, If progress is missing after a restore, confirm the active Windows account, storefront/profile, cloud state, and exact directory first. Restore the untouched backup before experimenting with individual files or older autosaves. SaveEditor.com only labels a game-specific editor as available when a separate linked Tool has a verified operational runtime; this reference page by itself is not an editor claim.