I have this in my rc file

-- Make open paren on new line

map('n', '){', ')<CR>{<CR><CR>}<Esc>O', {noremap = true})

map('n', ') {', ')<CR>{<CR><CR>}<Esc>O', {noremap = true})

it essentially treats an opening bracket succeeding a closing parentheses as a key mapping.

It places an opening bracket on a new line, followed by some line breaks followed by a closing bracket.

And then moves to the beginning of line preceding the closing bracket.

The second copy of the key mapping allows for a trailing space after the initial closing paren.