NHF – new heroes for Heroes V 3.1.

You didn't quite understand, the string isn't saved in the editor (which needs to be copied) until the mod is placed in the data folder, or until it's embedded in the map.

And the mod will be constantly changing, so embedding it directly into the map isn't always beneficial.

Here's what I wrote above:

That's what I'm telling you, the main thing is that the file with the heroes is available, and where it's located doesn't matter (in mods, in data.pak, or in the map), as long as it has the correct extension.
The fact that it will be constantly changing is not a problem; you can upload it with a fix, replacing the files on top of the old file with the heroes.
...
The paths to the heroes shouldn't be like that + one error in a character (missed a comma or an extra space) will not give a result.