- You were an hourly warehouse flunky, not any sort of professional programmer. While doing your warehouse job, you cobbled together a mish-mash of software stuff, on company computers, to try to make your job easier. With you there to fiddle and debug and update as needed, that worked pretty darn well.
- Now, you are leaving. Your layman's understanding is that the company legally owns all the software you made...as is. There ain't no "You Programming, Inc." in this situation, for your old employer to have any documentation, nor warranty, nor support contract from.
- Your suggestion is that the company delete the software, and revert to the previous procedures - which worked perfectly well. If it seemed worthwhile, a professional programming company - which could offer documentation, warranties, support, etc. - could probably duplicate the features of your stuff pretty quickly.
The goal being to convince the management of Warehouse, Inc. to order the deletion of your software from the company's computers.