In addition to creating or updating records in Salesforce, whenever a form has submitted the data from that is stored within a Submission in Formstack for Salesforce itself. If needing to delete these submissions, this can be done through the Submissions Dashboard.
First, log into Formstack for Salesforce and click on the Submissions button for the form containing the submissions to be deleted and then click 'View Submissions'.
Next, place a check mark next to the Submission (or Submissions) that need to be deleted and click the 'Delete' button that will become active once at least one Submission has been selected.
A pop up will appear confirming that you'd like to permanently delete the submission and clicking 'Yes' will complete that deletion.
Note: Deleting submissions from the Submission Dashboard will not result in any records within Salesforce itself being deleted or changed.