I don't think there's a way to undo a key when entering a sequence of keys.
Usually one would enter C-g to (keyboard-quit) and reenter the sequence
because sequences are typically short.
Documentation for keyboard-quit:
Signal a quit condition.
During execution of Lisp code, this character causes a quit directly.
At top-level, as an editor command, this ...
Now I get the idea, C-i is the same thing as TAB character so binding it to a function is a little tricky. this anwer worked for me. Here's the new config:
(define-key input-decode-map (kbd "C-i") (kbd "H-i"))
(define-key evil-visual-state-map (kbd "H-i") 'evil-insert-into-lines)
In your doom init.el file you need to enable format +onsave in the :editor section. See the snippet below or look at the example init.el (with format +onsave disabled) on the doom emacs git repo
(evil +everywhere); come to the dark side, we have cookies
file-templates ; auto-snippets for empty files
fold ; (nigh) ...