First, I’d be sure you’re actually using full_url in the action element of the form.
If you are, then you may need a version upgrade for the login API to accept a next query parameter. That could have been added at some point, though I’m not sure without looking into it deeper.
I will say that I actually verified you would do this, I checked it myself, so I’m sure you can on a recent version of Jupyter (2.1.4).