When you edit a .txt file in construct 2 the changes are not saved.
Project file: https://www.dropbox.com/s/w7dnjmdy0b34u2k/txt%20file%20bug.capx?dl=0
Right click the "File.txt" within the projects window and then click open. Erase the "Test 3" line and then save the txt file, then close it. Now the save button in construct is greyed out and you are unable to save the project.
I think this is a bug because you should be able to save the project after changing the text file.