In my view you can't have it both ways - if you want efficiency it's not reasonable to expect to be able to hand edit the data in a text editor. Especially since at the scale that efficiency matters your text editor is going to struggle.
If you don't care that much about efficiency then CSV, JSON, XML all provide perfectly good solutions and they're actually more easily editable in a text editor than what is being suggested. It's also much more sensible if you are hand-editing tabular data to just slurp it in to a jupyter notebook and do the edits there and shoot it back out because it means you've got a straight forward record of what changes you've had to make and can re-run those changes at a click of a button.
If you don't care that much about efficiency then CSV, JSON, XML all provide perfectly good solutions and they're actually more easily editable in a text editor than what is being suggested. It's also much more sensible if you are hand-editing tabular data to just slurp it in to a jupyter notebook and do the edits there and shoot it back out because it means you've got a straight forward record of what changes you've had to make and can re-run those changes at a click of a button.