In order to disconnect your Shopify store from Gelato please follow the steps listed below.
From the Shopify dashboard click on 'Settings'
A new page should pop up.
First, click on 'Apps and Sales channels' and follow up by clicking on the 'Uninstall' button in the Gelato app panel.
Gelato app shall appear in the "Uninstalled" apps list where you can reinstall it if needed.
You can confirm that your Shopify store is disconnected when in the Gelato dashboard it changes from this:
to this: