Enabling context menu and customization for Cards of the same

As a product owner and manager, i would like to have see the context menu for each cards in the Next gen project Board and customize the context menu as well.

As of now i am able to see only "Add Flag" and "Add Label" and no provision to include other options.

For example: I would like to have another option as Change Assignee where i can assign or change an assignee.