On my Macbook Pro with High Sierra 10.13.3, I have an Apple external keyboard. I used
System Preferences > Keyboard > Modifier Keys... to make
CAPSLOCK into another
With this configuration, I can move one Chrome tab to the right with
CAPSLOCK-TAB, very convenient.
However, moving one tab to the left with
CAPSLOCK-SHIFT-TAB doesn't work on the external keyboard.
It does work on the laptop's built-in keyboard, oddly.
This is not Chrome's fault, because I see the same behavior in the Sublime Text app.