Version 0.4 worked perfectly, there were no alignment issues and chest slots worked fine as well.

I have both OptiGUI and Polytone installed.

Namely, the following UIs are bugged for me:

• Chest slots and slot highlights inside small chests, big chests, ender chests, minecart chests and barrels:

• Furnace and Blast furnace:

-Librarian slot highlights:

• Lastly, are boat chest textures supposed to look like this? Are they still a work in progress, or are they also bugged?:

Regarding the slot highlights, they are unfixable, they simply render wrong, this was the case for durability bars but it got fixed in the last update. but since fonts aren't made to be used this way it's unlikely to get fixed like the bars, both the slots and tooltips are experimental so i will experiment, adding a small outline to this aswell, can help with visibility.

Regarding the Furnace and blast furnace, i have gotten that issue 4 times and it seems i didnt manage to completely fix it i will keep looking into it.

Regarding the chest boat, that is also unfixable as minecraft uses the item name for the chest boat so i cannot rename it's ui to a new texture.
It is however part of the polytone mod extra features.

Alright, sounds good. Thanks for the quick reply! Love the pack:)

can you tell me what language you were using with the broken furnace?

Sure! I was using English [Chest Slots] (US).

got same bug on 1.21.1

chest boats are vanilla now,
furnaces are fixed, although mod compatibility has to be readded with polytone
slots can only be mitigated separate issue is dealing with that specifically