To link to a chosen heading (= reference) in Google Docs, you can copy the heading's URL after clicking on the chosen heading.
If you paste that copied URL somewhere else, it will ask you to fill it with the doc's name by pressing Tab:
and it will not show to which heading it points to unless you hover over it:
Since it is much more readable if you add the full line of headings afterwards to that main document name as the only name of the link, you may end up in linking like this, so that you do not need to hover over it:
You will often run into a line break:
See MY_DOC_URL_LINK --> "my sub heading1" --> "my sub heading2" --> "my sub heading3 that is linked in the link" with an insight into the topic.
The quotes are to show where a heading ends before the next text goes on, that is better to read, no matter whether it goes on in the same line or starts as a new one afterwards, but there might be a better default than this format.
Is there a plugin or built-in tool that lets you copy the path of headings that you need to jump through from the Test1 Heading until you reach your chosen Test12c heading? You could then just paste it after the URL as a string (and reformat it a bit as you like, or get a format from that tool so that you do not need to add --> and "" for each level):
An answer would already be if someone knew how to get the heading path from top to bottom of a chosen heading. I could not find this, if you right-click in the SUMMARY pane, you only get the browser menu, which does not help getting the needed heading path of the chosen heading.
Not only such a menu is not there, but you cannot even mark the headings and copy them from the SUMMARY pane.