Hi DEVITA,
Normally, the Assembly items will turn into Bundle items in QuickBooks Online. This type of item doesn't have COGS since this is just similar to Group items in QuickBooks Desktop. However, the COGS account will remain in the inventory items, so they are still reported to COGS when you record sales for them.
The SOS Inventory you mean, I think that's the Inventory asset account assigned to your items. You can check that out by going to the Gear icon, choosing Products and Services, and hitting Edit on one of the inventory items in a bundle.
By the way, the Assembly is one of the limitations in QBO. You may want to check others here.
We're just right here if you need additional help, so please feel free to keep on posting questions.