The problem with how we currently develop is, IMO, low control over screen space. We have files, which are strongly linearized. We can open more than one file side by side. Most tools provide some way to jump across references. Some tools provide these as inline inserts ("popouts"), instead of opening more files. But still, for any given thing you're focused on, most of the file you have on your screen is likely unrelated.
I'd love to see an experiment around such code bubbles, but taken to further extremes. Make it easier to pop up bubbles with a single function, that can optionally be expanded to cover more - and also, importantly, shrunk down to cover less. Let me see and retain the graph of connections on the screen. And edit code directly in these bubbles. All on a densely packed, 2D slate, scrollable in both dimensions and fully navigable with a keyboard.