New Feature: now you can assign a shortcut key for Tab Duplication in Edge insider Canary

Microsoft Edge Version 82.0.456.0 (Official build) canary (64-bit)

you can do it from here: edge://flags/

Assigns the shortcut Ctrl+K to Duplicate Tab

By default, both Ctrl+E and Ctrl+K are the shortcuts for Focus Search. If enabled, Ctrl+K is assigned to Duplicate Tab. – Windows

#edge-use-alternate-duplicate-tab-shortcut

and you get this when you right-click on a tab