@mekell would be great if you file an issue here Issues · plone/mockup · GitHub ... I suggest that pat-autotoc generates random numbers instead of sequential ids at the end.
Actually both following problems should be taken into account:
Requesting /@@theming-controlpanel#autotoc-item-autotoc-2 doesn't position the form in "Custom Styles" as expected.
Wenn the "Save"-Button in "Custom Styles" is pressed, the form is requested again and the page goes to "Themes". This requires the user to click "Advanced setting" and "Custom Styles" again every time it saves it.
I've filed an issue-1457958733 and I suggest to place further comments there.