For anyone still looking, I found a better solution for my use case. Similar to what Eric Hanko suggested, you can create a shortcut specifically for "Duplicate Tab" in Iterm2 that is much more direct, and replicates the "duplicate tab" functionality that I was used to coming from Terminal.
- Navigate to Systems Preferences > Keyboard > Shortcuts.
- Select "App Shortcuts" in the sidebar.
- Select "Iterm.app" from the Application dropdown.
- Type an exact match for the menu item to shortcut, in this case
Duplicate Tab as of the time of writing.
- Add the shortcut. I used
CMD + D.
NOTE: any shortcuts you create in System Preferences will override shortcuts already defined in Iterm2. This could lead to confusion later if you forget where your shortcuts are defined and get unexpected results using shortcuts in Iterm2.
Again, thanks to Eric Hanko for paving the way here.