Extra tubes

Although you can often achieve the appearance of an extra tube attached to an extra tube by bending the tube in a creative way and having a portion of the tube run over top of another tube, it is currently not an option to select another extra tube as the attachment point. I will consider adding this to a future update.

Having the option to connect any tube would be great. I basically can't add connecting tubes that would act as gussets as is.

I assume what you mean is that you can't add an extra tube to act as a gusset for an existing extra tube. This is true. However, to be clear, you can add an extra tube to act as a gusset for any of the tubes in the main triangle. Here's an extra tube acting as a gusset for the underside of the down tube.