In Casey's mod of 4Coder modal_n (esc n) does a jump to next error. But how do you do a jump to previous error?

Also how does he do a vertical delete/kill as he calls it on stream?

goto_prev_error is not bound in Casey's config, but you can bind it yourself.

I think rectangle edits are an alpha feature only available in the power version of 4coder (and I don't know if there is a way to get access to that version currently).