Gadget headings don't have an ID set

Open the Dashboard page and inspect the HTML. You'll see that the gadget headings don't have an ID set. This makes it hard to target them from an anchor. Moreover, this leads to an invalid table of contents and can break the PDF export (XWIKI-20599). Try this content:

{{toc/}}

{{display reference="Dashboard.WebHome"/}}

You'll see that the table of contents anchors don't have any target (href="#"), which means you cannot jump to a specific gadget heading from the table of contents (i.e. scroll the page to that gadget).