Stephan�� this is very cool, I had a similar idea for a system browser with code cards similar to what you have implemented. In my case I was thinking single column , keyboard driven like yours but also several icons and visual coding :)
I was having the idea work like a workspace and then enclose the code with a shortcut to convert the piece of code to a block , then another shortcut to covert it to a method , etc. Also the ability to save multiple cards as a view preset that can be quickly brought back (abit like system browser navigation history) and many more ideas.