In this Preferences page, you can specify where files will be stored in 4gl projects created by the New 4gl project wizard:
By default, the second option is selected, and source and output files are separated between two folders with the corresponding names - source and output:
If you choose the first option - Project folder - all the files (both source and output ones) will be stored in the same folder - the folder of the project:
With the second option, you can specify your custom names for the source and output folders as well: