Adobe hasn't released the SCSS files for this one, so it's a bit tricky.
Please try the linked CSS. There are quite a few changes I made, so test it before using it please.
From a CSS perspective, you can also add the following to your CSS:
body.media-desktop div.frontpage-function-buttons div.grid-buttons>div:first-child:nth-last-of-type(1){margin-left:23.75rem}body.media-desktop div.frontpage-function-buttons div.grid-buttons>div:first-child:nth-last-of-type(2){margin-left:17.8125rem}body.media-desktop div.frontpage-function-buttons div.grid-buttons>div:first-child:nth-last-of-type(3){margin-left:11.875rem}body.media-desktop div.frontpage-function-buttons div.grid-buttons>div:first-child:nth-last-of-type(4){margin-left:5.9375rem}
This CSS selects the number of elements (buttons) you have. And if it is 4 or fewer (the bar can accommodate 5 as the class is grid-5) it amends the margin of the first element to center align.