Customizing Superfish - an article explaining how to adjust transparency, arrows, borders and drop shadow properties for the Superfsh add-on.
To disable a certain page's link, just set a Don't Link in Navigation custom attribute on the page. You can do this by putting the page in edit mode, then clicking Properties > Custom Attributes. Select "Dont Link In Navigation" from the dropdown, check the new checkbox that appears, and click Save.
This is useful for making your top-level pages act as categories that aren't landing pages themselves-- while still letting the child pages be clickable as usual.
The superfish block works like the default autonav block in that it picks pages based on how they show up in your sitemap. It is possible to create a custom menu by using "aliases": internal links concrete5 can create so you can have one page be linked in multiple places.
If you're using the Greek Yogurt theme on your site, you might notice some odd spacing between menu items and other issues with how Superfish looks. This is because Greek Yogurt is a little "greedy" or "strongly typed" and has a few rules that interfere. Luckily you can deploy a custom override for your site that corrects these issues.
Download superfish-greek-yogurt-override.zip and extract the archive. Place all the files and folders inside at (your site root)/blocks/superfish and you should be all set.
If you're not familiar with overrides in concrete5, check out Change Things Without Hurting Anything: Overrides.
Thanks to mkly for putting together the override.