The specific question was "How do I set up depreciation on the portion I rent?"
As you correctly said, you have to manually enter the rental square footage percentage by yourself which is the second option Business use percentage above.
TurboTax does not automatically carry over the rental deduction percentage into “Percentage of time I used this item for this business in 2020 (e.g. 80%)."
Excellent point clarifying that percentage of time = rental square footage and that property insurance also requires a specific adjustment!
