Was it clear what the iconography in the Trait Tracker was intended to represent?
It was clear and the tooltip was explaining the icon well.

Did it make sense in the context of crafting and vendor windows?
I didn't compare the two.

Did you typically use the regular UI, or Gamepad Mode?
The regular UI.

Was it clear when an item had been successfully transmutated?
Yes, that icon is also clear.

Do you have any other general feedback
I like that we see directly which items can be researched. An addition it would also be very helpful (since we can't just show a specific item item, e.g. medium belts), to have an indicator that shows how many reasearchable items of that type and trait we have in our inventory.

For example, if I haven't researched anything yet, and, lets say, have 2 invigorating light helmets and 5 training light helmets in my inventory, plus lots of other items which might get in betweens those helmets due to their item name. If I am then in the deconstruction window, I don't want to look through all items and count how many of the researchable ones have the same trait. I just need one of them for research, the rest can be deconstructed. The way it is, the sorting can be very tedious, more so, since we also see all items that are stashed in the bank.

So, my suggestions would be to add a small number, or something similar, next to the magnifying glass for unkown item traits. The number would say how many, e.g. light invigorating helmets I have (in the above example ?2, as marker for both items - ? is just meant as a placeholder for the actual icon). This should probably be context dependent, so inside the inventory it only counts the corresponding inventory items, on a crafting station it would also count the banked items.