saving files logicaly?

I dont understand how the save feature works, with other design type software I usually open the last version I was working on, then save it as a new name ( usually with the date ) and then carry on working. I know then that I can always go back to yesterdays work irrespective of autosave.
With Arduino I end up with folders with the new name pde file, which is blank, and the orig pde file ???
If I try to just save, it tells me some things are read only so I must pick a new name and so on..

I have done a search but can find no explanation of how it works, any pointers anyone?

Examples in the libraries are read only. Create your own sketchbook location, see FILE > PREFERENCES menu.

thanks Rob I will try that