When using a file selector inside a qmlproject then it will not find any locally imported directories inside the QML included in that file selector. When opening the QML file it will state that it cannot find the import. For the instance of the file not in the file selector it works fine.

In the attached example, check both instances of the A.qml file, one will find the components import fine and the other will not. This is also a problem in Qt Design Studio.