Alternative World Save Location (Forge)

Requires the library mod Collective.

Alternative World Save Location allows users to change where Minecraft saves (and loads) its worlds. When you've got multiple modpacks or instances spread out in different locations, you can easily lose track of your data. When transferring to another PC or OS install, you might forget to copy over your precious world. With this mod, you can keep them all in a single location. Preferrably in a folder that's automatically synced to the cloud. Your old saves will be where you left them, and you can copy them over to the newly set location.

By default it does nothing so it can be safely installed and left alone. When you want to change to a custom saves path, you'll need to edit the config. Enable 'changeDefaultWorldSaveLocation' and input your custom path in 'defaultMinecraftWorldSaveLocation'. As a path separator (between folders) use either two backslashes ( \\ ) or one forward slash ( / ). See the images below for a how-to.

Configurable: ( how do I configure? )
changeDefaultWorldSaveLocation (default = false): Disabled by default, to prevent unwanted modpack behaviour. When enabled, changes the world location to 'defaultMinecraftWorldSaveLocation'
defaultMinecraftWorldSaveLocation (default = "%instance_folder%/saves": Use either \\\\ or / as a path separator. The location of the folder containing the world saves.

changeDefaultWorldBackupLocation (default = false): Disabled by default. Enable this to set a specific world backup folder. If disabled, this will be set to 'defaultMinecraftWorldSaveLocation'/_Backup.
defaultMinecraftWorldBackupLocation (default = "%instance_folder%/backups": Use either \\\\ or / as a path separator. The world backup folder if both 'changeDefaultWorldSaveLocation' and 'changeDefaultWorldBackupLocation' are enabled.

It's very simple!
Here we've got a folder with a single world save called "Adventure!".
It's located outside the Minecraft instance folder, in "C:\Minecraft\Saves".

To enable our client to find the external saves folder, we edit the config file.
Set "changeDefaultWorldSaveLocation" to true.
Change "defaultMinecraftWorldSaveLocation" to "C:\\Minecraft\\Saves" OR "C:/Minecraft/Saves".
Both two backslashes and a single forward slash are support as path separators.

Save the config file and load the Minecraft client.
Your old saves will be where you left them, but the game now reads world save data from the path you've input in the config file!