thanks, yes, i saw this but given the date (opened in ~2017?) I thought I had missed something, as this request has been there for years and there are more like this and the problem still remains.
For immediate improvement: Note that decreasing font size (i.e.Ctrl + Minus) does, as far as I can tell, have the effect that more information can be displayed in those hover windows (as they don't shrink at the same rate as the rest of the UI & font size). I don't know if decreasing the font size is a feasible option for you, or if you were already aware of this behavior.
Also, for warnings and error messages or documentation, if you want to read them more in-depth, there's always the option to look at the documentation from cardo doc --open or at the warnings and errors from manually running cargo check or cargo clippy in the terminal. I personally also quite often keep a terminal window open next to my vscode window anyways for more readable error messages, where I can run a tool like cargo-watch or bacon (I randomly found the latter a while ago and like it quite a lot).