Extending an extended blueprint

I'm struggling with the blueprint extend syntax as per https://learn.getgrav.org/16/forms/blueprints/advanced-features

How can I extend a blueprint which is extending another? Quark-open-publishing theme extends the Quark theme. I'm wanting to extend Quark-open-publishing, but the blueprint that gets extended seems to be Quark's base. There doesn't seem to be any documentation around the context blueprints:// syntax to know where to put in the explicit reference to which 'blog' blueprint I wish to extend.

I just proposed some documentation for it, ostensibly the same as here: /forum/forms-blueprints/importing-blueprint-does-not-work-what-does-context-do-mean-t8418?u=olevik.

You'll need type to refer to the file, and context to resolve to Quark Open Publishing. Are you streams setup as such?

Ok, thank you! Got it working now with

extends@:
type: item
context: user://themes/quark-open-publishing/blueprints

Your comment on /forum/forms-blueprints/importing-blueprint-does-not-work-what-does-context-do-mean-t8418 was the most helpful for me, always best to see an example or two (I hadn't come across that thread in my searching yesterday)