I suppose you are trying to develop a package since you are interested in having a src folder?
Try looking at 5. Creating Packages · Pkg.jl on how to automate having a structured folder for development,
Thanks. Just right off the bat you have helped me. Actually I am not trying to develop a package. I just thought I would need a src folder because I have seen src folders elsewhere. But if I do not need a src folder where do I put my source files? Right in the environment folder? Could I still create a src folder as a subfolder of the project folder and put my source files there for better organization?
An environment is not really tied to any file/folder structure, you can also have your source files using a specific environment in a completely different folder and just activate the correct environment by pointing to it.
You can create a src subfolder or simply put the source files in the folder of the environment (the environment is just specified by the Project.toml).
I would still suggest you to try and generate a package structure for your tests, it directly creates a source subfolder and allows you to then re-use your code when you think it is in a good state by just using it. On top of easing up an eventual publication of your experimentation for other people to use.
You are right. Learning how to create packages is in my agenda. However, my previous attempts failed. I took note of the URL you recommended and will give it another try ASAP.