To remove a Form from your dashboard the workflow owner (1) first needs to uncheck "Publish Form on Dashboard" from the sidebar menu.
Then delete the spreadsheet from the Dashboard (2)
My Form is no longer linked to a spreadsheet
If a Form on the Dashboard is no longer linked to a spreadsheet please proceed as follows:
1. Search the spreadsheet name in your Drive, as it appears on the Dashboard
2. Start Form Workflow Plus on this spreadsheet
3. Click Create on the Set up tab
4. Once a Form is linked uncheck Publish Form on Dashboard
5. Refresh the Dashboard https://app.formworkflowplus.com/forms.
Requesters will no longer be able to access the Form from their Dashboard