The bar inside the custom groups is visible, but the bar in the regular tabs is completely invisible. it still works, it just doesn't display.

Tested with alloy forgery in isolation.

What versions of the game, which loader, which version of owo... Ideally a log please

0.11.1 with qfapi - issue doesn't occur with fapi. https://mclo.gs/AABAP8v

Can confirm this happening in Minecraft 1.20 with QFAPI 7.0.4, owo-lib 0.11.0, and Quilt Loader 0.19.1. The issue does not manifest unless an owo-item-group is registered, as including any arbritrary mod I.E. Ecotones, then everything works like normal. If I add Alloy Forgery or Mythic Metals the scroll bars disappear.

Its worth noting that the "Search Items" tab keeps its scroll bar if an owo-item-group is present, although from what I have seen it cases with more mods it can be somewhat inconsistent on what groups get a scroll bar or not.

Fixed in 5317684, scheduled for timely release in 0.11.2