I assume that was a joke, but if you want custom glyphs for programming language digraphs and keywords, you might be able to do it with "sym-lock.el" for emacs. (I haven't used it in a very long time, but I remember it could be used to replace TeX backslash sequences with the corresponding symbol.)
> Now, because this is essentially just in-font magic, copy-pasting the first rectangle should lead to you pasting the plain string "~", and copy-pasting the second rectangle should lead to you pasting the plain string "custom".
