Yes, you can connect more than one Shopify store or Amazon stores for multiple regions (US/Canada/Mexico, pan-EU, etc) into one Inventory Planner account.
Note that adding more connections or stores to your Inventory Planner account will commingle vendors and purchase orders. If you want this information to show separately, you will need to set up a new Inventory Planner account.
To connect a second store, go to Account > Settings
> Connections > Connect Another Platform.
You will then be asked if you want to create a new account or to connect to an existing account. If you want product, vendor, and purchase order information all showing in the same account, then select an existing account. If you want all information separate, then click on 'Create new account to start fresh'.
For more help with store set-up and warehouse configuration, check out our article with more detail to connect your store.