No 'Execute' button available in the Overview for WorkFlow under Service Catalog
Other WorkFlows have the option.
In the Overview in ECC, the Workflow type is defined as 'Application Deployment Workflow'
The 'Application Deployment Workflow is for Release Manager Workflows.
If the current client isn't a Deployment Client,
The Template for Standard WorkFlows(JOBP) used in this Client has the 'Deployment' flag set. Any new WorkFlows created will have the same settings.