Google has rolled out account-level sitelinks to save time and ensure your text ads show with the additional links. The account-level sitelinks can show with any of the ads in your account.
“Sitelinks show additional links to specific pages on your website and are an effective way to drive traffic to your business. To save time and help ensure your text ads show with these helpful links, we’re rolling out account-level sitelinks: sitelinks that can show with any of the ads in your account. Campaigns and ad groups that don’t have campaign or ad group-level sitelinks, respectively, will automatically use sitelinks created at the account level.”
However at present all advertisers do not have access to these links. If the advertisers are not using sitelinks at campaign or ad group level, in this case all future sitelinks will be created at the account level automatically.
“To add more links to your ads, create sitelink extensions. Sitelinks can take people to specific pages on your site—your store hours, a specific product, or more. When someone clicks or taps on your links, they skip right to what they want to know or buy.
When your your sitelink extension appears with one of your ads on a computer or tablet, it shows 2 to 6 links. When it shows on a mobile device, it shows up to 4 links. Sitelinks appear in ads at the top and bottom of Google search results.”