How can I change the unit of an item that already has a unit without delete and create that same item?
The developers of the application don't provide technical support to public users. Firstly, if you have the software installed go to Help > Contents and read there about the available options withing the software. If you can't find anything, then use the following link to get in touch with the developers: http://www.neptonglobal.com/contact-us.html