Multiple products at once

Create all the products for which you want to follow the stock (as stockable products). Once the required products in stock have been defined, use an initial inventory operation to put the current quantities into the system by location. Go to Inventory Control ‣ Inventory Adjustments to start your initial inventory.

Give it a name (for example Initial Inventory) and select the stock location of your inventory. Note that when you select a parent location (such as Stock, which might be split into sub locations), you can also select the sub (or child) locations.

You can choose between making an inventory for all products, for a few or only for one. In this case, we choose the All products option.

From https://www.odoo.com/documentation/user/10.0/inventory/management/adjustment/initial_inventory.html