While reading through the bug-list I found some bug-reports to be adressing the same bug, well...
BugID: #0137 is NOT a bug!
The thing is that you have to press ctrl+left/right button in order to elevate/lower the terrain further. Keep in mind that the scroll-lock must be turned OFF.
It took me a while to figure out, but seeing some of the custom maps available - I cannot possibly be the only one
Well, I looked for the BUG report thread, but failed to locate it... so I made this post. Fearing that the topic is hopelessly outdated I'm wondering if the bug report is being updated?!? (I found a lot of nice info on some of the stuff I've encountered in the game - - - very comforting!)
Hmm, signing off with a feeling of being last with the old news...