switch to split screen in IntelliJ (ideaVim)
Ctrl
+ ww
is a quick way to switch between windows. (Works for me on linux/intelliJ)
You can use Ctrl-W + h/j/k/l to navigate splits as in the original Vim. Ctrl-Wh should work. If it doesn't for you, check File | Settings | Vim Emulation and your ~/.ideavimrc config for some keyboard shortcut clashes.
There is one known issue when one split has a row of open tabs that is higher than the row of another split, then you cannot switch to it due to the miscalculation in the window coordinates.