I'd like some general actions, defined in sapphire-extension.xml to be available only through a key binding in the whole editor.
Works fine when there's no context set to the action but then there are a locust of redundant buttons scattered around.
Is there a hint I can't find for hiding the action's button?
It seems rather peculiar. For instance, I would be concerned about how users are to discover these actions. I think I would want to see multiple adopters raise a similar requirement before moving forward with putting something like this into the framework...
I'll describe the case just as an example:
I've implemented a Find dialog which searches the XML content and selects the relevant outline node.
Understandably, users wish for the dialog to be available by key binding from anywhere in the editor.
If I am understanding your scenario correctly... Another way to look at this problem is that key bindings are local-only. Once you've focused on a property editor, you loose key bindings from the editor page. If this wasn't the case, then you could add editor page level action (you'd get a button in the header) and the key binding would work everywhere one the editor page (unless local context's action shadows it).