Unfortunately, you cannot change the default path to save projects every time. This requires a manual selection as you have been doing.
However, there is a sort of work around. First, create a folder in the desired path (such as on the desktop, in a certain folder, etc.) and save that Kickstart project there.
Then close KickStart, go to the path and open your project directly from the folder you saved it in. This should open KickStart automatically with your project loaded on screen. Run a test or gather data, save, and export. Check the export and it should be in this folder along the path you desired.
