It is currently not possible to override context values on a per-component level. In your context provider component, you could use a Default to formula with a test-value from an attribute first, and then your actual value from an API or whereever you get it. As long as you never set that attribute in production, then the test-value would only be used in the editor.
It is a little hacky solution, and there might be other ways. Let me know if it is a bit confusing, then I can set up an example.
There will be much better options for working with test-values in the future of nordcraft, but it is still mostly conceptually sketched out, so still a while away from implementation.
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