Mins theme sidebar restrictions

I understand that the theme supports only three sidebars:

Footer 1
Footer 2
Footer 3

But I desperately need to add a fourth on the post page so that visitors can more easily be directed to specific posts by date, topic, etc.

I’ve tried three different plugins, including Widget on Pages, but nothing will let me add a sidebar that actually appears on the side of the page. Sometimes it appears at the bottom of the page, and the formatting is wonky —?text is not aligned and is sized oddly.

Is this because it’s an old theme that isn’t especially good at working in Gutenberg or Beaver Builder?

Help.

The page I need help with: [log in to see the link]