undefined reference to main - where to start finding the problem (question)

[Anonymous_Banned275]

After "Add exiting directory" to a project I get this error.
Obviously coming from the "add" , I can guess that , however my question to the forum, is

how / what to utilize in QtCreator to FURTHER identify location of the complaint. Usually clicking on the error opens the actual location of the problem.

Not this time.

This error actually opposite I get by adding another "main" to the project.
That one is easier identifiable.