If you're looking for alternatives to the Ren'Py Save Editor, you can try:
Most RenPy games let you skip read text (Ctrl or Tab). Combine with "Skip Unseen Text" to speed through replays.
Once you've loaded the save file, you can view and edit the saved data. The Save Editor displays the saved data in a tree-like structure, making it easy to navigate and edit. renpy save editor
In UnRen's popup menu, select "Enable Developer Console" (option 5 or similar). Some versions auto-enable.
Politely ask the developer to add New Game+ or chapter select. Small indie devs sometimes listen. If you're looking for alternatives to the Ren'Py
If you prefer not to download third-party software, Ren'Py has a built-in developer console. Many games disable it, but you can re-enable it:
Caution: This can break scripted sequences if you jump incorrectly. Make a backup first. If you prefer not to download third-party software,
If you prefer a GUI:
Note: Many modern RenPy games use init python classes or custom objects. The GUI may show them as <__main__.MyClass object>, which you cannot easily edit.