You can go back to add or delete attributes even after you have created the master product.
To change attribute title, code, or description
1. On the Manager product attributes page, select an attribute (System Setup > Set up commerce web components > Manage product attributes).
2. Click the Edit icon located in the Actions column at attribute setup.
Note: Clicking Edit will not allow an administrator to add values to attributes.
3. Edit the attribute's title, code, and description.
4. Click Update Attribute to save changes.