We tested this on the Next-Gen Update (Version 4.0+). The tool handled the new scripts and variables without crashing. We managed to edit a Level 60 NG+ save and a fresh Level 1 save with equal success.
The most famous and powerful tool is (often called "Witcher 3 Save Editor" on Nexus Mods). However, "exclusive" versions refer to:
To access the save game editor, PC players will need to: