I use Emacs with Vertico for completion and want to center the minibuffer content on my large monitor to avoid constantly looking at the left corner. After trying various solutions unsuccessfully, I finally found GitHub - mpwang/perfect-margin: [emacs] auto center emacs windows, work with minimap and/or linum-mode , which allows me to set the minibuffer margin effectively.
(add-to-list 'perfect-margin-force-regexps "*Minibuf")
(add-to-list 'perfect-margin-force-regexps "*which-key")