.4rpl files are simply normal text files with a different extension, they can be opened with any generic text editor. The community frequently uses Notepad++, but the default Notepad program will also work.

After trying to open a 4rpl file a window will pop up asking you to set a program to open the file with. This pop up will show up every time you try to open a 4rpl file until you have set a file association. This particular pop-up does not have the ability to set the file association (for whatever reason), so we'll have to manually do that by creating a .4rpl file ourselves and setting the association manually.

• Make sure you have file name extensions enabled in the Explorer ¹⁾
• Go to your desktop
• Right click and select “New > Text Document” ²⁾
• Give the file any name, but replace the .txt bit to .4rpl (click through the warning message)
• Right click the created file and select “Open With > Choose another app” ³⁾
• Make sure the “Always use this app” checkbox at the bottom is checked and then click the program you want to use. ⁴⁾
• If your preferred program is not in the list click “More apps” to expand the list. If it is not in that list you'll have to select “Look for another app on this PC” at the very bottom and directly specify the .exe of your program.
• You may now delete the file. Pressing the from within the game should now open the file in the editor specified by you.