Issue 638347  has been merged into this issue.

I believe the following should do the trick:

Instead of simply going back with:

    window.history.back();

You can first see if the SHIFT key was pressed, as such:

    !e.shiftKey ? window.history.back() : window.history.forward();

Thanks

 Issue 638605  has been merged into this issue.

 Issue 639312  has been merged into this issue.

Right now, with the latest version of the extension shift+backspace is performing the same action as backspace.  This is confusing.

Fixed in version 1.5 of the extension, landed as https://chromium.googlesource.com/chromium/extensions-by-google/+/05efa01c40b34bf3d1aa32662663caee1155773d

The same fix also made sure ctrl-backspace and alt-backspace are ignored by the extension.