I was going to mention holyC here, but I don't think it is the same thing. holyC lets you embed images etc in the code, but those images don't become part of the logic. This paper is talking about mixing graphical programming languages with textual ones (like a file with both scratch blocks and c code in)
Yeah I'm not talking about that. I'm thinking more like "a C program is just a parse tree, so why couldn't a visual tool help you visualize or rearrange the parse tree?"
This academic paper assumes two largely unmixed disciplines just barely kissing each other. I see a complete blending coming that will melt the boundaries between textual and visual programming.
Once you start thinking like this, you stop seeing semantic editing as a feature of a particular language: it should just be a native ability to have on any parseable code: the ability to reassemble the parse tree nodes like lego bricks.