While you upload a WSDL for the creation of a Logic Apps SOAP Custom Connector, you may get the following error:
'The validation of the WSDL document failed. The errors are: 'Error event: 'WsdlImportRuleImportNotSupported', message: 'WSDL Import is currently not supported.'. '.'. Status code: 'BadRequest'.
This is because the uploaded WSDL document is using the import feature (i.e. it points to another WSDL document for a fragment of definitions to import) which we do not support at this time. However you can use a tool to flatten the WSDL documents into a single file without use of import. Here for instance is an old post by Jason Shuler of such tool: http://www.shulerent.com/2013/03/14/generating-a-single-flattened-wsdl-from-an-existing-wcf-service/