Now that you have the proper category setup, you can begin to add transactions. Since this data isn't received from a linked account, it will need to be manually added. To do so, follow these steps:
1) Click the "Expense" tab.
2) Click "Add Transaction."
3) When naming the transaction, name it according to the type of lost inventory. For example: Damaged Product, Lost Product, etc...
4) Choose the category "Lost Inventory."
5) In the description, put as much info about the loss as possible. This is for your reference and will allow you to easily distinguish between different "Lost Inventory" transactions.
Again, we are not tax professionals and therefore encourage you to contact an accountant for more information.