Divider Element: When you change orientation to vertical using percentage(%) as a unit on the height renders nothing. It just does not work. I have tried everyting and I believe it is a bug or short coming.
A saw this issue discussed month/years ago but no solution was offered.
Still not working in 2025! @timmse
That won’t work in 2030 either 
If you specify a height of 25%, the height refers to the height of the surrounding wrapper. However, this is 0. According to Adam Riese, 25% of 0 is still 0.
To use 25%, you would have to give %root% a fixed height, such as 100px—the line within %root% would then be 25px high. However, I don’t see the point in doing that… 
Divider is now working fine. @timmse explanation not even necessary but thanks anyway.