How to move in insert mode in vim?

https://vi.stackexchange.com/questions/10296/navigation-in-insert-mode

If you just need to modify a small amount of text or a word, you can use <Ctrl-O>h/j/k/l.

<Ctrl-O> takes you back to Normal mode just for that command, and then drops you back into insert mode, so it saves you some amount of key presses, if you need to go into normal mode for a small movement.