Ordinarily a CMakeLists.txt is situated at the root of a project, however when using a horizontal code sharing structure the root CMakeLists.txt can often be defined in a sibling tree.

e.g.

/some_app/CMakeLists.txt
/some_app/src/

/some_dependancy/CMakeLists.txt
/some_dependancy/src/

where /some_app/CMakeLists.txt has the dependancy defined as :

ADD_SUBDIRECTORY(../some_dependancy some_dependancy_build_dir)

In this case, the dependancy's CMakeLists.txt doesn't appear in Creator's project tree meaning it needs to be edited externally.