How do I add an entire directory to a QT creator project

The simplest way is to directly edit your .pro file, add HEADERS += mydir/*.h and SOURCES += mydir/*.cpp and the contents of the whole directory will show up in QT Creator. Further reference: http://qt-project.org/doc/qt-5/qmake-project-files.html

Open a terminal, navigate to the folder where you want to have you project file, and then run the command

qmake -project

This will search the current directory and all subdirectories for files with extensions such as .c, .cpp, .h, etc. (the full list is found by typing man qmake).

But keep in mind that it will overwrite your current .pro file if you already have a project set up.