Backup your work to avoid losing everything.

Use a proper merge tool (like WinMerge, or the Visual Studio Code Extension L13 Diff ), to merge between folders, and update modified vanilla files to a new vanilla patch.

So choose a prefix no one else will ever use like the name of your mod.

Your files can have any name, all files in the folder will be loaded by the game. Adding separate files and use loading from folders whenever possible, to improve mod compatibility and maintenance.

Minimize overwrites of vanilla files, unless that is your main goal or somehow necessary (on_action triggers).

Read the forum post by the developer for more info.

Use CWTools for advanced validation and auto-complete: CWTools is a syntax validator for Stellaris modding, developed as an extension for Visual Studio Code and also available for Sublime.

Note that some modifications need a game to be loaded or even the option to be used on screen/in the back-end before their code will run. Good Editors usually have the ability to track changes to files from outside the program and prompt for a reload, thus showing you errors with one glance at the file.

Use the error.log file to get execution errors: The log folder can be found right next to the mod folder.

A good text editor can also format the displayed text so that braces can be collapsed if complete, and complete/incomplete pairs are highlighted.

Use a good text editor (recommended: VSCodium or Visual Studio Code) to edit files and search into multiple files.

Create a mod for your modifications: use a personal mod even for small changes, and never directly modify the game files in the Steam Stellaris folder, as they may be overwritten without warning.

Hoi4 color change mod