The process is the same in both games. But, game mode JSONs are located here in Reborn: C:\SteamLibrary\steamapps\common\Erannorth Reborn\Erannorth Reborn_Data\StreamingAssets\Content\GameModes

When editing a mode, i.e., 'Ironman,' manually, it's highly recommended to set it up as a "mod":

i.e. \Content\Mods\My Custom Modes\GameModes\Ironman.json

Otherwise, any changes you make to the vanilla files will be lost when you verify game files through Steam or if Steam decides to do it automatically. And you can have all your modes there. If it's a brand-new mode, you must also add an entry for it in a ModLoaderUser.conf file.

ModifyGM is a good way to adjust a few settings, as it does that for you. It clones the vanilla mode as a mod with the values you’ve tweaked, allowing you to play with the mode just as you normally would. The modding guide has a list of the most common settings.

The mod created by ModifyGM can also be edited manually. For example, if you want to modify a vanilla mode but the original JSON is missing newer settings, your export will include them with default values.

F10 (right after launching the game)
ModifyGM [Mode Name]=>[setting]=>[value]

引用自 ER Raven：

The mod created by ModifyGM can also be edited manually. For example, if you want to modify a vanilla mode but the original JSON is missing newer settings, your export will include them with default values.

F10 (right after launching the game)
ModifyGM [Mode Name]=>[setting]=>[value]

Thanks for the reply

This is what I did for Chronicles. The example you gave was:
ModifyGM Spicy Vanilla=>ChallengeRating=>6

However, I'm not sure what to put for [setting] or [value] since I don't know what the defaults are and I don't wan to change anything until after I export it to the JSON file. With chronicles I exported campaign and knew it was 5 by default so it was easy to just do the above, but change the spicy vanilla to campaign and 6 to 5

Indeed, many of the settings in Chronicles, like this one, don’t exist in Reborn. Most default settings aren’t included in the vanilla mode files either, often because they aren’t needed or don’t work in Sandbox, whereas they might be in Gauntlet and vice versa. For example, Ironman.json contains 33 settings lines out of the 128 possible for Reborn.

To manually export and tweak a mode using ModifyGM, you could use a setting like MinEncounterNormalNum, which sets the minimum number of non-elite enemies and works in all game modes. A setting of 3 is relatively safe for all modes, too. So, you could do something like:

ModifyGM Ironman=>MinEncounterNormalNum=>3

Or whatever mode you want to clone. In this case, Ironman mode will be exported with all its default fields vanilla (3 happens to be its default value; it doesn't really matter if you modify something or not) and ready to be tweaked. If you need any help on any fields missing from the modding guide, feel free to ask!

So I was able to export the file and make changes like I've done with Chronicles, but they didn't seem to take effect. Is there something different than Chronicles with this?

It’s hard to say without more details. As long as you exported the JSON file using the Reborn editor, or ModifyGM, edited its values with the correct data types (int, float, string, etc.), and restarted the game, everything should work.

Double-check that all these steps were done correctly. Also, make sure that the changes you made are actually supposed to produce the effect you're expecting.