Something which I found lacking is ways to go from beginner pages to more in-depth ones
For example the page on partial functions does not link to anything !
Neither to the stdlib definition nor to the spec of pattern matching anonymous functions
And more generally where to find information is sometimes inconsistent
For example I was not able to find a page about enums in the Scala book, but there are two pages in the reference (the first does link to the second however), and a page in the stdlib
I remember having a lot of trouble finding the stdlib docs (for Scala 3 for sure, for Scala 2 maybe as well) until I learned to add api to my search
(It is a simple trick, but I would not expect beginners to stumble upon it)
Overall, I feel everything I use (and see used, for example in users) is properly documented somewhere for both beginners and experts, but those are usually harder to find than they need to be.