RimWorld saves all configuration file (base-game & mods), savegame, presets, logs, etc. in your user-folder. In some instances it can be useful or necessary to redirect the location of this folder, which the game allows via a simple start-up parameter. The Readme.txt in the game's install-folder already has all the instructions to achieve that, so we're just repeating them here for the ease of access.
There are a few reasons to redirect the user-folder - most of them are rather niche though, so unless you have good reasons, it's nothing you really have to - or should - think hard about.
Installing the game on a portable drive
While not exactly a good method - you can install the game on a portable hard drive or even USB-stick and take it with you to play on other devices without having to install it locally. In such a case you can redirect the user-folder onto the portable drive to take all your settings and saves with you.
Using multiple individual mod-lists at the same time
If you want to use different modlists/setups at the same time and your mod-configs are differing between them, running the game out of one user-folder can be a problem - you technically have to change mod-settings each time you switch your modlist/saves. To avoid that you can make multiple installs of the game each with its own user-folder or even use only one install of the base game & mods and just have different shortcuts on your Desktop to start the game from different user-folders. While this works; mod-managers like RimSort are able to make 'instances' of the game with the same benefits as well - and depending on how tech-savvy one is, this could simply be faster and easier to achieve that way.
This are the original instructions by Ludeon as they can be found in the game's Readme.txt.
Startup parameters can be added in different ways, so following we will just go over each method and explain how to access the input.
"-savedatafolder=C:/New User Folder"
Shortcut
If you start the game via shortcut on your Desktop (not the one created by Steam!) you just right-click the icon, choose 'Properties' and then switch to the 'Shortcut'-tab. In the 'Target' field just add the start-up parameter after the file-path - and make sure to leave a space between!
Steam
If you start the game through the Steam client, or via a Desktop shortcut made by Steam when you installed the game, you have to enter the parameter in Steam as well. Right-click RimWorld in your Steam Library and select 'Properties...' - it will open the 'General' tab by default already. Under 'Launch Options' just add the command and close the menu again.
RimSort
In RimSort, first go to 'File' and then 'Settings' to open the settings menu. There just switch to the 'Game Launch'-tab and input the parameter there. There is also additional information to be found there about the use for other parameters if relevant.
WIP