How to map i to start editing on visual block mode?
I want the same behavior for <shift>-i and i.
You can use :h map-expression to determine which version of visual mode you are in, and change the behaviour accordingly. Visual mode mapping
vnoremap <expr> i mode()=~'\cv' ? 'i' : 'I'
will make i act as i in visual and linewise-visual modes, and as I otherwise, i.e. in blockwise visual mode.
