I would like the ability to export the neighbor list to a file that I could then download and import into Winbox's address list.

It is already possible. You need to write a script that parses "/ip neighbor print" output and adds neighbor addresses to address list.

How do I programmatically access Winbox's address list for editing??

if router has neighbor discovery turned on winbox loader should be able to find that router in your ethernet. as that is how far neighbor discovery works.

if you have larger network you want to monitor and login use the dude, if you are concerned about traffic that will generate just disable all the monitoring, so you have your device map.