What is the difference between "design variable" and "project variable" in HFSS

There is a project manager on the left. http://www.edatop.com/uploadfile/201...2051020167.jpg

The variables when you click on Project1 are project variables, and you define them by using a dollar sign, they will work for every design or every material definition etc. The variables that come up when you click HFSSDesign1 are design variables. They will only work for things that are defined inside HFSSDesign1.

Correct. The project variable is especially useful if you want to study the influence of material parameters (e.g., dielectric constant).