Add New File to Project Dialog
File > Project Files > Add New File. ****See also: Adding Files, Base Locations, File Types, Library Configurators.
All new files are created directly in the project folder and use the project folder as the base location.
See Adding Files, Base Locations for the explanation.
Filename. The extension DOES NOT define the file type and format.
This is not to say that there are no default extensions. They exist but do not matter to TIDE. See the File Types topic for more.
Type. This selector (and NOT the extension) is what defines whether this file is a BASIC or C source file, a header file, HTML file with BASIC or C code inside, and so on.
Format. For configuration files you will also need to select the format, i.e. the kind of the configuration file you are adding.