Not exclusive to the 64bit version, the quick navigation feature has been around for a while and what's new now is the ability to disable it via that option you've found.
It refers to the back arrow that shows up after you navigate to a different point of your code:
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It'll show up when you:
- Hit F2 and select a different sub/function
- Right click a sub/function name in your code and choose "Go to SUB/FUNCTION (name)"
- Right click a label name in your code and choose "Go to label (name)"
- Use the bookmark features in the search menu or via keyboard shortcuts
The back arrow is supposed to work like a browser, allowing you to go back to the spots in your code where you were before a jump to another section. When you hover it you'll see what line is next in the navigation history:
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