I'd like to implement something like Highlight Usages, but on a wider context and scope.
When I invoke my new "Extended Highlight Usages", the usages are not only shown in current editor, but also in all other editors, and new editors that are opened after that.
The highlighting should not disappear after the regular "Esc" invoking, like it does for Ctrl-Shift-F7.
I'm not sure about the UI, most likely I'll provide an intention to add/remove the target of some reference from the current "Extended Highlight Usages" set.
I'd like the set of current active highlightings to survive a project reopen etc.
Any API pointers to get started?