How do I insert a linebreak where the cursor is without entering into insert mode in Vim?

if (some_condition) {[ ]return; }

:map g i[Ctrl+V][Enter][Ctrl+V][Esc][Enter]

:map g i^M^[

f}i^M^[O

:s/{/{r/

:map g :s/{/{r/ ^M :s/}/r}/ ^M

:map <C-m> i<CR><Esc>h

:map g ^f{malr<CR>`a%hr<CR>`a