XML source formatting does not work with plugin.xml sources

I have a normal eclipse plugin project with a plugin.xml file. Since I am using sonar radar with XML validations, I want the file to be indented in a specific way.

Eclipse XML auto-formatting is not available when I view the XML using the plugin-manifest editor (by clicking the plugin.xml source tab at the bottom of the editor)

I have already tried to set up hotkeys in eclipse to trigger formatting in this particular context, but I cannot find the correct context.

Automatic formatting in this editor is simply not possible or am I missing something?