Yes, you can add a new variant to an existing product that is already published on your Shopify store. There are two ways you can achieve this.
First method: Creating the variants directly from the Product Detail Page in Gelato
Find the product you would like to add variants to your store and click on Edit Product > Edit Design
In the sidebar on the left of the Product detail page, you will be able to select the new variants (new sizes or colors, etc.) and adjust the design if necessary.
Publish the changes
For this to work, the product must be created from the Gelato Dashboard. All variants must be connected and not ignored. Additionally, all variants must be connected to the same product type. This means it will not work if one or more variants are not of the same type (e.g. Some variants are posters with frames, some are posters with hangers, and some are posters without frames).
Second method: Create the variant in Shopify and connect it to Gelato
Create the new variant manually in Shopify, e.g. by clicking on "Add variant" or by duplicating an existing variant - see screenshots below.
In the Stores section, select the correct store to view all the products and click on "Sync products". After a while, you will see a new variant as "Not connected".
Connect the new variant to Gelato as shown here.
If you need to add many variants, it might be faster to create the product from scratch following the steps described in our article How do I add Gelato products to my Shopify store?