I need to add an option in my theme options panel to set a specific custom menu's links all to nofollow.
Does wp_nav_menu() allow this or does it require a custom walker to manually ad rel="nofollow"?
As you can see above, the Advanced Menu Properties are hidden under the Screen Options pull down tab located in the upper-right corner of WordPress Dashboard.
NOTE: Make sure that you are in the Menus screen:
W.r.t your question, the Link Relationship (XFN) option is what you want "check". Then the appropriate field will show up for each menu item allowing you to define its relationship (
rel="____"). You can also leave it blank for some items (meaning, no relationship will be specified).
Some years ago there was the only reason to use
rel="nofollow" attribute on internal links — PageRank sculpting. These days are gone forever.
If you don't want some pages to be indexed, use a plugin (e.g. WordPress SEO by Yoast) to add
<meta name="robots" content="noindex, follow" /> to the head section of these pages.