I feel max encumbrance needs a buff. I'm level 16 with a max encumbrance of 36. I am being returned to town every 26 seconds because of full inventory.
As someone into retro computing I appreciate the style of the UI. I'm glad you thought to include a dark mode to. With a little reshuffling or just more room in general I think it could be further improved. I should also state I'm using v1.3.4 in the browser.
For example if the equipment section was 1-line taller it would eliminate the need for any scrolling. Perhaps you could move the encumbrance bar into the equipment area, remove its heading, and eliminate the empty margin between them. Similar to how the HP and MP bars are in nested into the Adventurer's Papers area.
Speaking of Adventurer's Papers area, the stats section is ~2.5-lines too short. Perhaps the experience bar could be moved into that area too.
For the lists that do require scrolling, I think a slight reduction in the scrolling rate would help. Presently, when I scroll in the Inventory or Knacks list, one stepping of my scroll wheel moves the list down an entire page. I personally find that a bit disorientating as it can make it hard to keep track of what line i was up to reading. I would prefer if it scrolled at something like 3-lines at a time.
I like how the "choice waiting" button vanishes when there are no choices. It would be nice if the "skill tree" button did the same. Having it vanish unless there are unspent skill points. It can always be accessed from the top menu if needed.
Moving the dedicated guild calendar button into the top menu would also help to reduce visual clutter and free up more screen space. It's not a feature I use regularly enough to warrant it's dedicated button.