Unsure if this is just this addon in combination with Super Duper Macro.
However, if I create a macro to toggle my bags as a floating macro (accessed by /click sdf_NameOfMacro)

Then enter right click mode in Neuron, and set an icon in there, with the code being /click sdf_Bags (in my case) the icon shows on the Neuron bar, but with a ? icon and unknown as the title.

This would imply that the icon selection is not working in Neuron, the title I would expect not to be shown as it is a floating macro and is code, not a spell being cast, but the icon should show if I have selected one I would imagine.

The bar:

The macro screen:

The code actually works as expected and opens my bags.
Shouldn't the icon be selected as I chose?

Yes the icon selector has been broken for a little while. I'll see if I can get that sorted for you

Is this still broken with 1.3.2?

I will need to revisit this, I have changed my UI again since, I will let you know when I get the time, If nobody else reproduces before me.