You can add your own comments in the project file to remind yourself of the purpose of adding a specific line of configuration, so that you won't forget why you added a line after not touching it for a while. A comment starts with the hash symbol (#) after which you can write anything since the build system will simply ignore the entire line of text. For example:
# The following define makes your compiler emit warnings if you use # any feature of Qt which has been marked as deprecated (the exact warnings # depend on your compiler). Please consult the documentation of the # deprecated API in order to know how to port your code away from it. DEFINES += QT_DEPRECATED_WARNINGS
You can also add dash lines or use spaces to make your comment ...
