It turns out that what I thought was a Godot optimization issue was so difficult to pin down because... it wasn't a Godot optimization issue. All my optimization was for naught! The issue was that Godot streams only pull one message off the queue per poll, and I was only polling once per frame, so 60 items would take a full 60 seconds to load. A simple while loop resolved all pop-in woes... oh well. At least it's better optimized now? That might save me some work down the line (like when zones get bigger or more full of items); doing things more efficiently is always a good thing.

With the time that freed up, I imported all the sprites for every item in the game and added support for the items in Forest Craft, Stoneworking, Herbalism, Gemcutting, and most of Cooking except for the progress items, plus all the special items like burrow certificates. There's still quite a few bugs to quash (like animations not playing), but only a few more skills (mostly metalworking) to go, and then I'll be going through the list of item interactions like the context menus, dragging from the inventory, etc. before returning to UI work.

(video snipped for dev sanity)