After I posted this, I did find the Pull from an API option and was able to authorize and configure it properly for Webflow. (Now just trying to get around NationBuilder’s limit of 100 entries for a return but that’s not a Parabola issue.)
EDIT: About the limit, looks like I’m able to cycle through the API results’ pagination: API Pagination Issue so trying that out now!
And your Mailchimp references will be super helpful, thanks!