Currently, you cannot. They were removed from Inventory Profit Margin report because of a bug. See Inventory Profit Margin report bug when Inventory Kits are sold for a discussion.
I don’t see a purpose for this. Inventory kits do not, by definition, exist until the instant they are sold. They are merely a convenience for selling pre-existing inventory items in a bundle. In that sense, they are very much like non-inventory items. That is, they are entry shortcuts, not separate functions.