>> Personally I hope that every "-other-window" command doesn't get an
>> "-other-tab" counterpart (to go along with "-other-frame"), but rather
>> that a single systematic method is developed, like the elpa.gnu.org
>> package other-frame-window. Ref eg
>>
>> https://lists.gnu.org/r/emacs-devel/2019-10/msg00261.html
>>
>> (AFAICS nothing has been implemented)
>
> Actually, this is already implemented, but without an obvious keybinding.
> This small patch binds a general command to 'C-x t t' (or maybe a better
> key would be 'C-x t w').
>
> Then after typing 'C-x t t' as a prefix key sequence,
> the next command will display its buffer in a new tab:
>
> @@ -1585,6 +1585,7 @@ tab-prefix-map
>  (define-key tab-prefix-map "b" 'switch-to-buffer-other-tab)
>  (define-key tab-prefix-map "f" 'find-file-other-tab)
>  (define-key tab-prefix-map "\C-f" 'find-file-other-tab)
> +(define-key tab-prefix-map "t" 'windmove-display-new-tab)

I see that using windmove-display-new-tab in tab-bar.el is inappropriate,
so here is refactoring: