Post Processing_Font Icons

{
    "type": "font-icons",
    "from": "assets/namespace/folder/etc",
    "to": "assets/namespace/font/font-id.json", "//": "Use assets/minecraft/font/default.json to modify default font",
    "mapping": [
        {"from": "\ue000", "to": "\uffff"}
    ],
    "textures": "assets/namespace/textures/font/whatever-this-is"
}

An advanced post processing pass that convert all font icons into a single font file. This is also the main reason why I choose to make Multipacks (because I'm tired of dealing with default.json).

For the configuration that is shown above, you'll have to add your-id-name.json inside assets/namespace/folder/etc with the following contents:

{
    "id": "namespace:your-id-name", "//": "This id is optional, but is needed to use with something that uses Multipacks Engine",
    "texture": "./your_icon.png", "//": "This path is relative to the JSON file location",
    "ascent": 8, "//": "Glyph ascending height, a.k.a the icon location",
    "height": 8, "//": "Glyph defined height. Use negative value for negative glyph width"
}

The folder structure with configurations above would look something like this:

assets/namespace/folder/etc/
 |-- your-id-name.json
 |-- your-icon.png