Anyone know where to find information about how to full take advantage of the SKSE UI functions? Particularly, I would like to know where I can find out about all the "target" string parameters for things like UI.GetInt()/UI.SetInt() etc.

So, when I see examples like:

UI.SetString("FavoritesMenu", "_root.Menu_mc.panel.message.text", "My Text")

Where did "_root.Menu_mc.panel.message.text" come from? I have read through all the packaged SKSE documentation, comments in UI.psc, etcetera - and I find examples but no explanation as to how all these submenus are organized, or how to use these functions myself.

You can get the "paths" for the target parameter from looking at the AS sources:
https://github.com/Mardoxx/skyrimui

Each menu is a separate movie. The top level element to access elements of the object hierarchy on the stage is _root.
The top level element of the class hierarchy to access static variables is _global.

As mentioned, you can get most of the names by simply looking at the AS. To know the name of the object that acts as the main menu container (usually all menus are organized like that), you might have to check out the .fla.

Then there's also the SkyUI repository you should check out to see if things haven't been renamed there.

Okay, thanks! A quick glance suggests I'll probably have to spend some time looking closely at these to figure out exactly how they work, but it is good to know where they are now

Also, I may as well just ask since you could probably tell me a lot faster than I can try to test and figure it out myself - will the crafting menu variables allow me to hook into the Enchanting menu too? Or is the Enchanting menu separate, and not available for interaction with the current SKSE UI functions?

Thanks as usual.

Crafting/enchanting/alchemy should be the same menu.

In general, the UI functions can access data of any menu, but not everything can be done with these UI functions. To clarify, I'm talking about Set/Get to access UI elements from Papyrus directly.
If you want to do more complex manipulations of a menu, rather do that from AS, define an interface of functions in the UI to be called from Papyrus, and a set of events the UI sends back.