In the app's sidebar menu, click Manual Connected Groups. Click Enable button if this is the first time you use this feature to create Inventory Groups.
Click Create a new Manual Group button.
Enter an Inventory Group name. This name is not visible to your customers. It just helps you to easily identify what the Inventory Group is created for what purpose.
On the Search Products sidebar, select all the products (or variants) that you would like to add to the Inventory Group. You can type the product title to search for the product (or variants). Click the Add button to put them into the Inventory Group.
Finally, click the Save button. A new Inventory Group has just been created.