When this feature is is selected, it takes the current file and sets it up as the default file that will be opened the next time you launch MecaStack. This is useful for a couple of reasons:
1) If you are working on a particular stack design frequently, then each time you launch MecaStack this same file will be automatically loaded. This saves you the trouble of going and opening the file each time you start working on MecaStack.
2) You can use this feature to save “Default” values that you would like to use most frequently. For example, you typically do work in a certain region and use the same codes and/or parameters (Wind speed, seismic, etc..) repeatedly, then you can enter those values into a file, and then “Save Current File as Default”. Now these will be the values present each time you open MecaStack. The entire file is saved as default, and so if you have any Geometry, attachments, etc.., those parameters are also going to be saved to the default file.