You can add missed floors and rooms to an existing project using Windows Explorer or Mac Finder before loading a project into Stitch. You can also use multiple cameras to shoot a large property and then combine multiple projects into one by copying floor folders.
If using one camera:
To add a new room or floor to an existing project, even if it has already been processed in Stitch, simply copy room/pano or floor folders on disk into the correct location. If there are any folder naming collisions, rename folders before copying to have unique names. A room/pano folder must always be located inside a floor folder and a floor folder must always be inside a project folder in order to be recognized by Stitch.
If using multiple cameras:
First, load each project into Stitch independently. Do all image manipulations and color corrections and then Export the project; that step will cause the generation of all photosphere images using the correct camera system file for that camera lens. You do not need to do any laser data alignment at this stage.
Second, perform folder copying the same way as if using one camera. After that you can do all laser data alignment. Do not do any image editing at this stage or that will erase existing output images. Additionally, the new output images may get generated using wrong camera file.