Question

How do I import/export the settings for multiple WordPress plugins from one site to another? Preferably throught the WordPress UI.

Answer 1

You can not.
Each plugin have your own type of configurations and only with a export and import of a mysql database can pass your settings to another site.

After export and import run this query:

UPDATE wp_options SET option_value = replace(option_value, 'http://__www.old-site.com__', 'http://__www.new-site.com__') WHERE option_name = 'home' OR option_name = 'siteurl';
UPDATE wp_posts SET guid = replace(guid, 'http://__www.old-site.com__','http://__www.new-site.com__');
UPDATE wp_posts SET post_content = replace(post_content, 'http://__www.old-site.com__', 'http://__www.new-site.com__');