Microsoft SharePoint Online column formatting which creates a button that downloads the currently published version of a document.

published-version-sharepoint-column-formatting.json

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",
  "elmType": "div",
  "style": {
    "visibility": "=if([$File_x0020_Type] == '' || [$_UIVersion] < 512, 'hidden', 'visible')"
  },
  "children": [
    {
      "elmType": "div",
      "children": [
        {
          "elmType": "a",
          "attributes": {
            "href": "=if([$_UIVersion] % 512 == 0, [$FileRef], @currentWeb + '/_vti_history/' + 512*floor([$_UIVersion]/512) + substring([$FileRef], indexOf(@currentWeb+'^','^')-indexOf(@currentWeb,'.sharepoint.com')-15, indexOf([$FileRef]+'^','^')))",
            "target": "_blank",
            "class": "ms-fontColor-gray200 ms-bgColor-white ms-fontColor-white--hover ms-bgColor-themePrimary--hover ms-borderColor-themeDark ms-borderColor-themeDark--hover",
            "title": "='Version ' + toString(floor([$_UIVersion]/512)) + '.0'"
          },
          "style": {
            "text-decoration": "none",
            "padding": "5px 35px",
            "border-radius": "5px",
            "font-size": "13px",
            "white-space": "nowrap",
            "border-width": "1px",
            "border-style": "solid"
          },
          "txtContent": "Download"
        }
      ]
    }
  ]
}