If I edit the code produced by RapidApp, then change the interface, will I lose my hand-edited changes?
Not if you understand RapidApp’s strategy for merging code. RapidApp uses a comprehensive strategy for merging code that it generates with existing code. In addition, RapidApp always makes a backup of your original file when files are merged. If the merge is unsuccessful, RapidApp displays xdiff, a tool that allows you to resolve problem areas by hand. You can help the merge process proceed smoothly by limiting your changes to the provided “user code block” areas, not making gratuitous changes (like reformatting for style) to the generated code, placing large bodies of code in external files, and so on. See “Code Merging” for more information.