App inventor currently does not give the ability to merge projects or to take a snippet of code from one project and add it to another. To overcome this Gareth Haylings
, one of our open source developers, has created a Windows utility call the "AI Project Constructor" which gives you the ability to merge any number of separate App Inventor projects into or one or more screens in a new project.
NOTE: WINDOWS ONLY
*Also see the Project Merge Tool
created by the App Inventor team which works on all platforms and merges two App Inventor projects into one project.