Thank you both for the feedback.
As noted on the pricing page these new tiers are coming soon which is why the experience when you reach the token limit is a little clumsy. We need to build out the Stripe integration to allow self-service upgrade and downgrade.
In the interim, it’s possible to upgrade to the old Pro tier using Old Observable if you go to your Team settings page there. This will give you a significantly higher daily token limit. (We’re also working on optimizing token usage and in particular doing automatic summarization so that you don’t hit the context window limit, which can happen if you have long chats or notebooks.)
The current limits are provisional but perhaps despite appearances they are already quite generous given the economics. 
As for turning a chat into a notebook, you can click the Fork button in top right corner to create a notebook:
(There’s also a hidden feature where you can view a chat as a notebook without converting it… but that’s not really supported so you’ll have to guess!)