This is surely possible.

You need to find the monospace whitespace characters (seems there's a few [0]). Then encode a compressed version of the logical diagram in the white space, steganography style.

Or do something with characters [1] to compress a lot of data into a tiny ball of hair at the end.

Draw.io smuggles the XML in a PNG which I've always admired.

[0] https://en.wikipedia.org/wiki/Whitespace_character

[1] https://en.wikipedia.org/wiki/Combining_character

Lovely idea! You're going to be fighting against editors and linters but it'd be a very cool proof of concept.