feeds importer importing from several sources
Yes, there is. The supported way of importing multiple sources for one importer is to attach the importer to a content type (which can be configured under the "Basic settings"). Attaching an importer to a content type means that a node must be created to import content. Since you can create multiple nodes, you can import multiple sources with one importer configuration.

Be sure though that if you are importing nodes (using the Node processor) that the nodes you create are of a different type than the node type that you attach an importer to. It is wise to create a new content type that is specifically only used for your importer.

See also my answer at https://www.drupal.org/node/2854548#comment-11948926 for more information about why you should not attach an importer to the same content type as the one you select on the processor settings.