The feature request is to allow the plugins to get/set data in the header of the worksheet (a children element named like the plugin in the <settings></settings> element or something similar) to share plugin's "global settings".
f.e. my idea is to store at once a list of global styles to use in WriterRegions, to have the style customizable, shareable and written at once for the whole document (not in every region).
The get/set functions should be available also from "Toolbar Plugins" (if this kind of plugins is planned)