The #1 requested mind mapping feature is now in the just-released Curio 8.4: mind map relationship lines.
Select two figures in your mind map, right-click then choose Add Relationship Line, and a curved line with midpoint will be added to your mind map pointing from the first figure to the second figure.
It's important to note that this relationship line is a real Curio line figure and thus supports all the normal line attributes such as labels, coloring, width, arrowheads, scaling, dash patterns, etc. Style it any way you wish using the Shape inspector. Add additional midpoints. Add one or more line labels. Make it curved, straight, or orthogonal.
Here's another new feature in Curio 8.4 that will make lots of customers happy. Normally when re-arranging nodes in your mind map or list, Curio maintains the styling of those figures. This way you aren't surprised by Curio suddenly changing your carefully tweaked figure styles. However, now if you press and hold the Shift key right before dropping the figures then they will adopt the style of the branch they are being dropped to.
You can read all the details here in our Curio 8.4 release notes. Enjoy! :-)
Curio will automatically alert you that the new update is available. Or choose the Curio > Check for Updates menu item to grab it now.
Lastly, I should note that Curio 8 has just received 4 out of 5 stars from Macworld UK! Fantastic!