Fixes#2512
Can add an arbitrary number of tabs.
Graphical behavior is unchanged for small numbers: the whole space if
filled with the tabs - they are enlarged if needed.
If there are more the mode switches to "scrollable".
This does not, however, look very differently (see screenshot with the
current tab scrolled out).
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Co-authored-by: Konrad Pozniak <connyduck@users.noreply.github.com>
UlrichKu