This is a pretty simple tool to use. Select your planet size, tax level, and then use the SWC City Designer and design your city. Either outputs work from the city designer (the http or just the code itself). Removing facilities work just as easy. Design a city that you wish to remove and then hit the remove button. To update taxes/planet size only just change which ever one and then hit the Add City Design button. As long as there is no design city design in the box it will not add anything, just update.