Control-click and mouse 3 (middle button / scroll wheel) click already open a new tab in the current container.

But, if you're someone who browses primarily using keyboard shortcuts, this just doesn't cut it.

I went searching and found this issue, which is still open:

https://github.com/mozilla/testpilot-containers/issues/245

    "Opening a new tab from a container window opens a normal tab and not a
    container tab"

I should note that the last comment on that issue was made in July, so I went ahead and commented asking about adding a setting to change the new-tab container inheritance behavior.