One of the effects of the Tax Cut and Jobs Act of 2017 was to eliminate many of the itemized deductions that make up Schedule A. Theft losses was one of them.
Now, only theft losses that are due to a federally declared disaster area by the President are deductible.
Because some of these itemized deductions that were eliminated on the federal level may still be deductible in a state, TurboTax still has the data entry screens.
Please see IRS Tax Topic 515 at https://www.irs.gov/taxtopics/tc515