After submitting a Service Catalog request, the 'close' button does not work. As a result, the user is unable to dismiss the current screen
This will come under customization. We do not support an entire Service Catalog via Agent Workspace.
As an alternative, instead of having an entire Service Catalog dropped on Agent Workspace, consider building custom UI Actions that submit Service Catalog requests. These UI Actions can then be placed on the appropriate form/table, like Incident, sn_customerservice_case, etc.