If they are depreciable improvements that affect your office (roof, furnace, etc.), you still enter them as depreciable assets.
If they do not affect the office (remodel kitchen, bedroom, etc.), they are not entered anywhere.
If they are "repairs", either to the office itself (paining the office) or affect the office (painting the outside of the house, fix a hole in the roof), then you enter it as a repair in the Home Office section.
