The forum structure & topics have been designed to cover as many areas within the "mechanical design" sphere as possible. However, I'm sure there's some areas that have been missed.
If you're browsing the forums and want to contribute, but can't seem to find the best area to start a discussion, please let us know. Maybe we can create an area of the forum devoted what you're interested in discussing.
The place to go to make your suggestion is within the "Help & Info" forum. There's a sub-forum entitled "Suggest a forum topic". Here's a link directly to that area.