Ok ... lets offtopic for a while then:
Functionality and usability can be objectively measured:
Im willing to agree on statement it can be measured ...
But since person who will do that will have to come up with criteria, and every person will give other criteria different value, its not really objective.

The game has a tutorial which explains all these concepts.
It would be quite madness to not include such thing.

AFAIR, Solasta sorts spells alphabetically.
Yup and that is one of hugest problems for me.

As i said, i require ... maybe even demand my own sorting, i dont care wich is better ... i need it the way i would sort it, nothing else will do.

Feel free to think about it as my ... obsession.

Besides, it doesn't really matter to me because spell icons are sufficiently big and colourful to immediately spot the one I need. This is a stark contrast with BG3, where spell icons are just some glyphs and all have the same background.
Matter of personal prefferences in case.

To me BG-3 glyphs are perfectly recognizable from each other, since they have so different collors and shape ...
In Solasta where you see nig and collorful icons ... i see just some sparkly and shiny mess.

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//Edit:
The point is that a good functional D&D spell UI doesn't need that many icons.
I dont think you need many icons ...
I mean in Solasta if you pick Magic Missile ... button for II. and III. level shows up ...
In BG-3 (now) if you pick Magic Missile ... buttons for I., II. and once we will reach level 5 III. level will show up ...
The system seems basicaly identical, the only difference is that in Solasta you just get some anonymous brown button with "II." on it ... here you get Magic Missile Icon with II. on it.

The upcast spells becoming their own separate icons and spells is not a good design.
A 13th level Wizard would have 7 identical looking icons of Magic Missile and every other 1st level spell. 6 versions of 2nd level spells, 5 versions of 3rd level spells...etc. quite a lot of icons.
This isnt true for at least 3 patches, wich would make it (if im not wrong) aproximaely 3/4 year.
Since spells stared pop-up windows with spell level selection.
And then the fact that D&D spellcasters constantly change their memorized selection of spells makes an auto placement on a hotbar in a whatever order a huge pain in the ass. I'm already constantly searching for my spells at level 4.
I can relate to this ...
And just exactly the same pain it would be for me, if hotbar would start automaticly sorting everything alphabeticaly without any option to turn that shit off. :-/
I dunno, when *i* change my spells, i usualy make it with some expected result in mind ... so i keep check on order i activate them, and i also see the hotbar so i can presume where shall i look for them to place them where i need them ...
But i gues where is no will, there is no advice. :-/
If you have to constantly search a UI, it's bad.
I cant agree with this statement ...
If "everyone" would have to constantly search in a UI ... then it would be bad.
But if "you" have to constantly search in a UI ... then there is quite good chance that you simply dont use it properly. :-/