@fingus, @Kuba77 and @gabs5807, it has been like this all the time: The row is filled with 4 icons in portrait- and 8 icons in landscape-orientation; the remaining gap is not large enough to fit another icon (minus empty borders to the screen edge).
But I see no corresponding issue filed, hence the main developer cannot be aware of your suggestion to optimise the layout:
P.S.: BTW, this conversation is completely off-topic for this discussion thread, hence please stop it and file a proper issue repost so it might become being worked on.