This is an old revision of the document!
.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 (a default program to open this file type with). 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 through that.
.txt
bit at the end to .4rpl
(click through the warning message)
You can always repeat this process to set a different editor as the default program to open .4rpl files with.