It looks like how the editor.ContentTab is rendered by from AEM's core.js client library. This client library lives in /libs, so it appears like there is AEM no configuration that you can configure to display custom values based on your requirements.
Take a look at: Configuration of the contentTab: /libs/wcm/core/content/editor/jcr:content/sidepanels/edit/items/tabs/items/contentTab cq.authoring.editor.core logic: /libs/cq/gui/components/authoring/editors/clientlibs/core/js/ui/ui.ContentTree.js
This is how I would implement this new feature, if really required:
Utilise the Sling Resource Merge to merge in additional configuration under /apps/wcm/core/content/editor/jcr:content/sidepanels/edit/items/tabs/items/contentTab
Create a new clientlibrary with categories of "cq.authoring.editor.core".
I hope this helps.
However, you will be overwriting AEM's default behaviour. Maybe in the next AEM updates, your changes will be incompatible.