Where do I model the sale of a home in the future?
You should model this in the Additional Cash Inflows section. If any portion of the sale is taxable make sure you separate out the cost basis (non-taxable portion) and the taxable portion as you see in the screenshot below. Note how the Growth Rate of the Home Sale cash inflow is set to 0%. This is because it is easier to separate out the taxable vs. non-taxable portion if you project out the future value of the sale rather than using the sale price in today's dollars.
Note that when the sale occurs in the program the after-tax proceeds are reinvested in 'Taxable' accounts pro rata based on their balances at the time of the sale.