Is there a setting that affects the buttons available for UI line-level entry? E.g. I noticed the Advanced Intercompany JE lines have a "move up", "move down", "move to top", and "move to bottom" button option, but my standard JEs do not. Is this just standard behavior or is there a way to expose these additional button options in other sublists?

I think if it's not there, you're just out of luck

Based on the headers of your image, I would guess that this was a customization that isn't available with NetSuite out of the box.