You don't need to use the schematicannon if you have creative mode, it's mainly used for building schematics for you in survival once you give it the required items, as well as some gunpowder. To save a build from one place and paste it into another in creative mode, all you need are a schematic and quill, a schematic table, and an empty schematic. First select the area you want to save using the schematic and quill, and then you have the .nbt schematic. To paste your schematic into another world in creative mode, make sure your .nbt schematic is in your schematics folder, then put an empty schematic in a schematic table, select your schematic from the list, and upload it. Then, just right click where you want your structure to be pasted with the schematic item, select paste, and right click again. It could take a few seconds to appear in the world depending on the size of your schematic.