Input "business use <50%" as a memo in the disposition property description on screen 17.1.  Then click on the Carryovers/Misc Info link above the disposition properties list on the left side of the screen.  Form 4797 input for section IV - Recapture of 50% or Less Business Use is next to the bottom of the sections.  Then don't forget to manually enter this depreciation recapture amount as Other Income on the appropriate Schedule C, etc. wherever it belongs.