Those volumes are hard to control even to me.
I think, at the moment the best way to get started is indeed to look at the provided examples and the tutorial, even if it's not written in really good style (but dunno
Anyways, I wouldn't be dissapointed about anyone who doesn't like the current picogen, as I know it's hard to tame, and practically inusable by non-programmers as for the heightmap-definition.
Btw, most entities have a bit of contextual help, even the code editor. E.g., for a heightmap, type "([Heightmap ] x y)", move your caret below 'Heightmap', and press F1. You should save your scene first, then the path will be relative to the scene-file's path