I have a method of doing this, which has worked for me in the past. Now I am running into trouble with it, in a client's database, in FMP 12. I am just wondering what methods other developers use when they want to do this.
This is a simplified version of the problem: The user has a created a record and added a number of child records to it, in a portal. (Say, an invoice with a number of line items.) Now the user wants to duplicate the parent and all of the child records, changing only the date on the parent record. (Say, a customer wants to order the same items, for several consecutive days.) All the orders are usually placed at the same time. (For example, on Monday, the user knows the customer wants the same order for Tuesday, Wednesday and Thursday). This kind of task is often needed in rental houses and hotel reservations.