Here's some feedback:

I ran into issues while tab-sorting. A few options at the bottom would refuse to be swapped around, it was very inconsistent. I had to create new empty tabs just to push them downwards until I could move the others.

New tabs do not accompany the cancel and deconstruct designators, present in every vanilla tab. I was able to add them using QOL, but it could be a default feature of this mod.

Dragging and dropping would certainly be better than all the clicking that it takes to organize. No idea how much work that could give you.

Being able to tell the game how to order a tab's contents would be great. That way I can have all spots of Misc come first, before every other item in there.

Created tabs don't sort themselves alphabetically admist the vanilla ones. I believe a better option than doing so is to have them separate from the vanilla, but not at the bottom, but besides. The compatibility added for Architect Icons is great, but could be even better if you could choose them right from the left-side column. Having them be positioned on the left side of the text there would also be better, since that's how our brain memorizes them once in the Architect Tab.

Lastly, on the same vein of separating vanilla from new tabs, assuming the dropdowns won't be changed for click and drag: The dropdown could be expanded, starting with two options: vanilla tabs or created tabs. Dropdowns could even be replaced alltogether with a pop-up window, like the icon-picking one.

The new Vanilla UI Expanded mod is broken on my end and still doesn't compete with the possibilities of this one. I don't know if looking into their code or talking to their devs can help you, but it has its own pop-up window system and the mod Personal Work Categories have drag and drop features for its configuration.