I'm pretty sure you cant. Resources are allocated per-context, and context work in a single thread at a time.
This prevents any sort of multi threading since you cant:
a. Do GL calls against a single context in multiple threads.
b. Do GL calls in different contexts and share the results between them.
So if you want to draw in two different windows, AFAIK, you'll have to use different contexts and replicate the work from one to the other. Or you can handle everything in a single application that draws to two different places in the same window and context.
EDIT: NVM, you can switch windows as L Spiro said