I wanted it to be a global behaviour. I use codemirror specifically because the ability to indent using a tab indent allows me to rely less and less on the preview pane; it becomes really easy to see which line is the heading, sub-heading, main text etc. Very helpful in long typing sessions.
That's why the lines not wrapping at indent is a bit of nuisance as it takes away the clean look of the document. But if it can't be helped I'll make do with what i have.
I think I'll raise a request on Github anyway. Hopefully in the next versions of the plugin it'll be fixed!!
Thanks