Retrieve related id / parent id in Aura component when override standard New button

Currently this is not possible , please vote the idea

Get parentId when overriding standard actions with a lightning components

This currently doable by overriding New button using  Visualforce page. So we can retrieve Parent Id or any record field in Visualforce page and pass it to the Aura component.The workaround that works is by wrapping it inside Visualforce page.

Basically it is the same for both Aura and LWC but I still put it here for my reference

Example for Aura component

<apex:page standardController="MyObject">
    <apex:includeLightning />

    <div id="lightning" />

    <script>
        $Lightning.use("c:lightApp", function() {
          $Lightning.createComponent("c:lightComp",
              { opportunityId:"{!MyObject.Opportunity__c}" },/*** here my parentId***/
              "lightning",
              function(cmp) {
                   // do some stuff
              }
          );
        });
    </script>
</apex:page>

Example for LWC

<apex:page standardController="MyObject">
    <apex:includeLightning />

    <div id="lightning" />

    <script>
        $Lightning.use("c:lightApp", function() {
          $Lightning.createComponent("c:lightLWC",
              { opportunityId:"{!MyObject.Opportunity__c}" },/*** here my parentId***/
              "lightning",
              function(cmp) {
                   // do some stuff
              }
          );
        });
    </script>
</apex:page>

Useful Link :

• Use Visualforce page in Lightning Component
• Lightning Components in Visualforce

Hope this helps.