Hi Arne,
I think there is no clean solution for this. You will have to find a workaround.
I tried this and it worked:
I created a link like this in a html textbox in the gridder:
0_1498082353669_Bildschirmfoto 2017-06-21 um 23.58.23.png
Then I added #chapter4to the end domain and it jumped down to the anchor.
You will probably need to build an extra navigation which has the ````#ancors````` in the end of the url.
Like in the example I sent you in the beginning.
I hope that was not too confusing :-)
Best!
Marius