You do not need to start a new inventory. 

You will create an item group called "Living Room Sectional" which consists off 5 Boxes/SKUS. The customer will only see the sectional but your warehouse workers will see the 5 skus.  QuickBooks Support Can help you set this up. 

Example: 

Item: Living Room Sectional

1 x SKU 62452 Corner

1 x SKU 62500 Left recliner

1 x SKU 62550 Right Recliner

2 x SKU 00020 Armless Chair