Can I customize where GlobalTill data fields are mapped to in Shopify? For example, can I map the GT Brand field to the Shopify Vendor field?
Custom mapping is possible in some cases but is not supported by GT Support.
For example, the GT Brand is synced to Shopify under a metadata field. The metadata namespace is GlobalTill, and the value is the brand as it is in GT. This is not something that shows up in the normal Shopify UX, but an experienced developer will know how to configure with your theme.