Currently, to update a field in Salesforce you need to select a form field to update it.

Could there be a custom option in the form field dropdown on Salesforce Object Field Mapping section where this allowed free text so we can hard code values.

Expanding this further where we can enter free text and bovine it with values from the form fields e.g. "Text {2509-c9ba-fce7}"
This would push "Text {2509-c9ba-fce7}" to salesforce where {2509-c9ba-fce7} is the view form that field ID.