[SalesForce] Navigate to an edit page of a specific record in a line item on a Lightning component which is embedded on detail page of a standard object

One way that will work is to add a "callback" attribute to the component definition. In that callback you can trigger a redirect.

Add this to your component:

<aura:attribute name="callback" type="String" description="Call this to communcate results to parent" access="global"/>

In your helper class you would call it like this:

var func = cmp.get('v.callback');
if (func){
  func(); //this has no params, but you can pass them if you like
}

Finally in your instantiation, define the callback:

$Lightning.use("c:AppContainer", function () {
      $Lightning.createComponent("c:App", {
        callback: function(){window.location = "http://www.somewhere.com";},
        otherattribute: "blah"
      }, elementId, function (cmp) {});
    });    

Oh and don't worry that the attribute definition is a string - the magic of Javascript takes care of that for you ;)

The beauty of component framework is events .You can make two components talk to each other via events .All you need to do is handle the event when the case record is created in another component and use Navigation to redirect to needed page

Here is sample component you need to create for that

Create a component like below

<aura:component implements="forceCommunity:availableForAllPageTypes">
  <aura:handler event="force:navigateToSObject" action="{!c.navigate}"/>
</aura:component>

The handler controller logic for same is as below

({
 navigate: function(component, event, helper) {
  var sobjectId = event.getParam("recordId");
    console.log(sobjectId);
    if (sobjectId.indexOf("500") >-1) { //Note 500 is prefix for Case Record
        var urlEvent = $A.get("e.force:navigateToURL");
        urlEvent.setParams({
            "url": '/case/'+sobjectId,
            "isredirect" :false
        });
        urlEvent.fire();
    }
  }
})

Drag this component on the case creation screen using community builder .