Hello,
I'm working on an OS type project and I would like to know how to
make text editing software. (You can type things and change color and size)
Thank you if you can help

This code could be altered for ease of use, but the idea is simple; you have a lot of costumes that represent certain characters (remember to name them the same character they represent), then make a list with every useable character, then use this code:

forever
if <key [any v] pressed?> then
set [counter v] to [0]
repeat until <key (item (counter) of [list v] :: list) pressed?>
change [counter v] by (1)
if <key (item (counter) of [list v] :: list) pressed?> then
switch costume to (item (counter) of [list v] :: list)
stamp
move to next spot
end
end
end
end

I can't ensure this code is reliable, but it's all I can think of. Hope this helps!

You could take a look at a tutorial. I reccomend using a pen text engine to display the text.