I pay for a rider on my homeowners that has each item itemized and separately valued. I use
Quicken Home Inventory Manager to keep an inventory with purchase price and values. You can even store photos for each item. I generate reports out of Home Inventory Manager that I send to my insurer for them to create the itemized list.
The challenge I run into is when I get new stuff or sell stuff, there isn't a great way to get a report of what's changed (adds AND deletes), which is what the insurance company needs. They get confused if you send the new report of everything.