Big Sign Writer

config/bigsignwriter/config.json

Contains the general mod configuration. Can be edited through the in-game config screen, accessible by default through the sign edit screen, or Mod Menu on Fabric and NeoForge's mod list.

config/bigsignwriter/fonts/

Folder where you can put custom fonts! You can create copies of the default fonts from the in-game config screen, which will go here.

Custom fonts are .json files, which contain a "name":"" field, an optional "characterSeparator":"" field, which can override which character(s) to use in between letters, and a "characters":{} field containing every large character and the normal character they represent. You may add additional characters, as long as what you want replaced is a single, type-able character. There's also an optional "credits":"" field for adding credits, and an optional "parentFont":"" field for explicitly defining which font to inherit characters from (based on filename without ".json", or built-in id).

When editing/creating large characters, it is important that each line is the exact same width to maintain alignment. Different fonts will have different widths for different characters, so it is a good idea to make these directly inside Minecraft, and then copy each line into the config file.

The default 'T' is a good example, the top line is 3 blocks, which are 9 pixels wide each, making for a total of 27 pixels. Each subsequent line has one block, then on both sides of the block there is 1 space (4 pixels wide), and 1 "no-break space" (5 pixels wide), bringing the total in line at 27.

To check that your alignment is good, I like to copy three blocks ███ onto both sides of each line, then modify each line until all the blocks are in line with each other.

A massively helpful tool to aid in this process is Symbol Chat, which adds a menu where you can filter every available Unicode character by their width, among other things.